Somehow this didn't surprise me. Glad you finally figured it out and yes back in time we always told people to shut off the internet when testing.I guess a lot more people get away with leaving it on these days because most up to date hardware can handle the multi tasking. My self I have other computers I use for the internet and my DAW is a recording workstation and that is all it is, so it's off line 99% of its life. 
 
I'm not sure if it's in Sonars documentation but running Latency Monitor should be a recommend practice for getting started with a DAW. 

Cactus Music
Somehow this didn't surprise me. Glad you finally figured it out and yes back in time we always told people to shut off the internet when testing.I guess a lot more people get away with leaving it on these days because most up to date hardware can handle the multi tasking. My self I have other computers I use for the internet and my DAW is a recording workstation and that is all it is, so it's off line 99% of its life. 
 
I'm not sure if it's in Sonars documentation but running Latency Monitor should be a recommend practice for getting started with a DAW. 

I agree.
It should at least be a sticky.

So can this be marked "solve" so other people with a similar problem can find the solution?

jkoseattle
I am having to learn about cow anatomy so that I can operate on the cow so that I can repair its lactation system so that it will supply me with enough milk that I can make a souffle. I don't want to know anything about cow anatomy. I just want to make a f--king souffle.

The only thing better than one cow is two cows. Create a separate user profile in windows for going online. That way you don't have to constantly disable items when you want to do audio. You can just switch users. Much easier.

I spent a bunch of time this morning trying to automate the enabling and disabling of the NIC, but wasn't successful. I'm just giong to do this:
 
Windows key-X
M
Network adapters
Right click the NIC
Enable or disable
 
The only remaining question is whether it's ok to stop playback, leave the Sonar project open, and turn on the NIC, do some internet stuff, then disable it again. Just sitting here typing this with the project open but not playing, my System and compressed memory shot up to 2 Gb again, so my project is just about to crash. I guess that answers my question. Exceedingly inconvenient.

jkoseattle
I spent a bunch of time this morning trying to automate the enabling and disabling of the NIC, but wasn't successful. I'm just giong to do this:
 
Windows key-X
M
Network adapters
Right click the NIC
Enable or disable
 
The only remaining question is whether it's ok to stop playback, leave the Sonar project open, and turn on the NIC, do some internet stuff, then disable it again. Just sitting here typing this with the project open but not playing, my System and compressed memory shot up to 2 Gb again, so my project is just about to crash. I guess that answers my question. Exceedingly inconvenient.

This should be ok.
Edit: I don't have this issue with my studio pc, which is connected permanently by cable.
 

jkoseattle
I spent a bunch of time this morning trying to automate the enabling and disabling of the NIC, but wasn't successful. I'm just giong to do this:
 
Windows key-X
M
Network adapters
Right click the NIC
Enable or disable
 
The only remaining question is whether it's ok to stop playback, leave the Sonar project open, and turn on the NIC, do some internet stuff, then disable it again. Just sitting here typing this with the project open but not playing, my System and compressed memory shot up to 2 Gb again, so my project is just about to crash. I guess that answers my question. Exceedingly inconvenient.

I have an iPad just for browsing so I can keep my DAW off the internet except when updating/downloading new installs etc. An Android tablet with a Bluetooth keyboard can be had for really cheap these days.

Zargg
 
This should be ok.
Edit: I don't have this issue with my studio pc, which is connected permanently by cable.

 
Oh, this PC is connected permanently by cable, not using wifi. 
 
Anyway, I am now unsure if this is resolved. I was working all morning on my piece with the NIC disabled, and for grins I looked in Task Manager, and lo and behold, System and compressed memory is up around 2 Gb, just like it's always been. This, as I've mentioned, is a precursor to a Sonar crash, and now apparently disabling the NIC and swapping out for a hard-wired keyboard did not fix it. At this point I immediately opened LatencyMon, and the DPC is sticking around 200, so all I know for sure now is that disabling the NIC makes LatencyMon happy. Nothing else is really solved yet.
 
Throughout this whole thing, the max hard pagefault time has been very high all along, regardless of the NIC card or Play synths or anything. Is that something I should be looking at?

jkoseattle
 
 and for grins I looked in Task Manager, and lo and behold, System and compressed memory is up around 2 Gb, just like it's always been. This, as I've mentioned, is a precursor to a Sonar crash,

I get it its your go to for a project crash  ! But did platinum actually crash "THEN"  ? if not then knowing every other time it did crash you can be confident that you have fixed your problem. and your "precursor" was coincidental !
 
 
If it did however crash "THEN" ! or you want to sort out the Precursor / hard page faults you can try this !
A)Precrursor
1) Open Resource Monitor
2) Click the memory TAB
3) Click the Hard Faults Processes Mini TAB ( So as maximum is descending )
4) You can use this as an additional tool to help identify  what is responsible for your precursor ! This is a powerful tool to display the nuts and bolts of whats going on in your PC !
 
B) LatencyMon HardPageFaults
My HardPageFaults are 0 all day long everyday !
Now Depending on how much memory your PC has lets assume 16gb, Knowing your project size and knowing you have 40% memory usage.
This is what i did:
1) Control panel >System and security>System>advanced system settings>Advanced TAB> "SELECT" back ground services > then click "CHANGE" virtual memory and make sure it is "NONE" / 0MB for any HDDs.
See how this goes, run latencyMon for 20min or until you get a hardpagefault.
If you do get a HardPageFault :
A)You may need to increase your RAM
B)You may need to disable programs that you do not need, which will free up more memory, and is highly recommended !
 

jkoseattle
Oh, this PC is connected permanently by cable, not using wifi.

 
I also use a different PC / laptop next to me for internet, my z800 has No AntiVirus and No Firewall. Its no big deal to switch something off for Audio Processing and back on again when needed you will get use to it real quick.
 

jkoseattle

Zargg
 
This should be ok.
Edit: I don't have this issue with my studio pc, which is connected permanently by cable.

 
Oh, this PC is connected permanently by cable, not using wifi. 
 

I just mentioned it, because not everyone has the same issue. Might be down to different HW.
Should not be takes as an advice!