I have changed the title back to indicate that FabFilter is probably the troublemaker ...
 
More info (from testing this on 2016.04) last night:
 
When used in Sonar all FabFilter plugins either cause immense drop-outs that hang the audio driver (independent of ASIO buffer size), requiring restarting Sonar or cause Sonar crash when starting play back.
 
This happens for VST2 as well as VST3 – apparently not all projects. Simple audio only projects seem to work, but when used e.g. in a rather small project using VSTi (1x Kontakt, 5x WAVES Element, 1x Z3TA+) it happens all the time.
 
Interestingly, FabFilter Q (which is still version 1.x) works. All other FabFilter plugs are version 2.x and do not work. No other plug-in from other vendors (NI, WAVES, IK, BOZ, …) gives me similar a problem (i.e. they all work in the troublesome projects).
 
What’s also interesting: When I tried to replicate this in Harrison Mixbus 3.3 only FabFilter Q (which is still version 1.x) shows up in the host and works. All other FabFilter plugs (Version 2.x) are scanned but silently rejected (for unknown reasons) and hence never show up in the host at all.
 
What's going on here? I alerted FabFilter support ...

Could you be having any licensing issues? Have you tried uninstalling all FF stuff, then reinstalling and running Sonar as admin to reauthorize?
 
I use Pro Q2 almost exclusively as EQ on everything, and Pro C2, Pro-DS, and Pro-MB on almost every project. I have never had a FF related crashes. Currently on the March update but I've had all versions and updates from X2 and on. Used FF since X3a and literally never had a plug of theirs crash my Sonar. 
 
Not saying that because I disbelieve you or anything, just that it doesn't seem likely it's a "generic" problem with FF/Sonar. 

Have you tried this suggestion from their website? 
 
http://www.fabfilter.com/...eration-on-my-computer

Thanks Sander,
 
I did uninstall and reinstall all FF and then a full VST scan. Same story. I did not ask me to enter any new license information. I might just try to deauthorize and reauthorize manually
I will also check on the graphic card. Thanks for the tip. I'll get back when I got a chance to try it.
 
This is very likely something specific and not a general FF/Sonar problem ...

Sanderxpander
Have you tried this suggestion from their website? 
 
http://www.fabfilter.com/...eration-on-my-computer

Unfortunately neither this nor updating the graphics driver helped ... FabFilter support promised to look into this next week ...

Back again, tracking down this problem after a reply from FabFilter support indicating it might be a combination of plugins ... and indeed it is: FabFilter + AD2 currently do not like each other on my system
 
Here are my new findings:

1. the problem only occurs when I use Addictive Drums AD2 as a multi-out drum VST in the project
2. so in the original project, I can disable AD2 and all the crashing with FabFilter goes away
3. I could reproduce this issue in a very small project, having only 1 bass track plus AD2. Here whenever I insert AD2, create all the routing, and insert either FF Q2 or FF timeless into the bass track, it crashes Sonar immediately (I did this to rule out my initial thoughts that using a Sonar template for AD2 might be introducing this, but apparently it is not)
4. I managed to get it to hang once and could write a *.dmp file from the task manager (all other times Sonar crashed completely)

 
So I really don't know who is the troublemaker here (Sonar, AD2, FabFilter, or Roland drivers) BUT in the crashing projects I can insert any other EQ plugin (NI, WAVES, IK, ...) and neither causes a crash - so I believe the first one to look into should still be FabFilter (who just received the same info from me).
 
I have prepared 2 directories on my dropbox which contain the Sonar projects, the Sonar minidumps, README.txt and one contains a 570 MB zip file with a task manager *.dmp file
 
In case anyone likes giving this issue a try or in case someone at Cakewalk is bored enough to look into this, PM me and I provide the dropbox links.

I can try to reproduce tomorrow if I can find some time. If you like,  PM me a link to the test project? Not sure that I can do anything with the dump file though. 

Rob[atSound-Rehab]
Back again, tracking down this problem after a reply from FabFilter support indicating it might be a combination of plugins ... and indeed it is: FabFilter + AD2 currently do not like each other on my system
 
Here are my new findings:

1. the problem only occurs when I use Addictive Drums AD2 as a multi-out drum VST in the project
2. so in the original project, I can disable AD2 and all the crashing with FabFilter goes away
3. I could reproduce this issue in a very small project, having only 1 bass track plus AD2. Here whenever I insert AD2, create all the routing, and insert either FF Q2 or FF timeless into the bass track, it crashes Sonar immediately (I did this to rule out my initial thoughts that using a Sonar template for AD2 might be introducing this, but apparently it is not)
4. I managed to get it to hang once and could write a *.dmp file from the task manager (all other times Sonar crashed completely)

 
So I really don't know who is the troublemaker here (Sonar, AD2, FabFilter, or Roland drivers) BUT in the crashing projects I can insert any other EQ plugin (NI, WAVES, IK, ...) and neither causes a crash - so I believe the first one to look into should still be FabFilter (who just received the same info from me).
 
I have prepared 2 directories on my dropbox which contain the Sonar projects, the Sonar minidumps, README.txt and one contains a 570 MB zip file with a task manager *.dmp file
 
In case anyone likes giving this issue a try or in case someone at Cakewalk is bored enough to look into this, PM me and I provide the dropbox links.

Probably the reason I've never run into this bug is because I never load plugins until after I am done tracking everything and have removed all of the soft synths (i.e., everything is audio-only). Certainly is strange that AD2 and FF would even interact since they are on different tracks altogether.
 
Regards,
Dan
 

I just tried this and can't reproduce it at all. I
1. started a new project
2. created an AD2 instrument with options "all synth outputs" and "midi source" checked
3. in the AD2 interface routed all instruments to their individual outs
4. added another audio track and put some audio on it
5. Inserted multiple instances of Timeless2 and ProQ2 on a bunch of channels, both AD2 and the "free audio track"
 
It's not crashing for me. Anything else I need to try?
Right now my bet is still on something to do with videocard drivers or a missing C++ library or something nefarious like that. It's obvious something is different on your system than on mine because it's at least not a general bug between AD2 and FF.

dcumpian
Certainly is strange that AD2 and FF would even interact since they are on different tracks altogether.

 
yes, this makes it really weird ... but having double checked and isolated the issue, this is exactly what is happening.
 

Sanderxpander
I just tried this and can't reproduce it at all. I
1. started a new project
2. created an AD2 instrument with options "all synth outputs" and "midi source" checked
3. in the AD2 interface routed all instruments to their individual outs
4. added another audio track and put some audio on it
5. Inserted multiple instances of Timeless2 and ProQ2 on a bunch of channels, both AD2 and the "free audio track"
 
It's not crashing for me. Anything else I need to try?
Right now my bet is still on something to do with videocard drivers or a missing C++ library or something nefarious like that. It's obvious something is different on your system than on mine because it's at least not a general bug between AD2 and FF.

you did just what I did - and I was sort of expecting it not to happen on your DAW (since nobody here reported anything similar)
 
the bad thing about it is that I updated the entire system to latest software and drivers based on these FabFilter issues and it seems to perform much worse now i.e. I also had a lot of crashes with Kontakt in the past 2 days (Kontakt never worked perfectly with my system, not liking the Roland drivers a whole lot, but it used to be more stable than that). It went as far as crashing at project open (which has been 2 yrs since I last had that) and that I could no longer delete K5 from the Sonar project (never happened before). Now I also have a reproducible crash when inserting NI Supercharger.
 
I strongly suspect something went south during the updating and having the system up to the latest state is not a stable combination.
 
On the positive side: I have several projects which I can crash repeatedly at the moment. I do have full system backups, and a restore point before the last graphic card driver update ... so all this should be possible to sort out. It will just take a LOT of effort.
 
I will also try to get a different ASIO interface to check on this. These Roland drivers seem to be hanging like a sword over my head ...
 
My biggest suspicion, though, is the new driver for the graphic card (ATI Radeon™ HD 5450 Graphics) - how do I tell a good driver from a bad one? Are there some settings in the graphic card options that could hurt me that bad?
 
EDIT: BTW, I had another weird one (several times): The master bus got deconnected from the main audio channel of the interface i.e. after Sonar crash project loaded, meters jumping but no sound ... reassign master bus to different output and back fixed it ...
 
So any suggestions on how to tackle the problem are very welcome, especially on the order of sorting things out. I kinda want to have an up to date system (and not rollback to 2 months ago), but it should still work ...