scook
It can't be a good thing. First report of this type. Is a virus scanner running? Might want to call support tomorrow.

Active turning off the virus protection install went smooth. I must say after all the good information I am glad I did the upgrade. Testing on my laptop has been successful and I can see how taking advantage of the new tools will help me create the music I want. Thankful to everyone that gave input and help me get off the fence, now to mention for a $125 

No issues here.  I probably do not use it as heavily as some users since I am a hobbyist not a full time studio, but my set up is rock solid.  The one thing I did notice is that the interface setup defaulted to WDM which causes noticeable glitching until I switched back to ASIO.  Something to be careful about.  I use an old Presonus FirePod interface.  I also have a Mackie 1640 with Firewire interface & analog sound board.  I haven't tried the Mackie with Platinum yet.
 
The Platinum opens ALL old projects fine even Pre-X1 projects.

I have now installed Platinum on my main system, the installation was flawless BUT opening projects took a while to open, Platinum has crashed twice with me using Kontakt 5 as a simple instrument when trying to make modifications to 8 Dio strings that I am using. An to add one audio dropout while makings changes in Kontakt also, should I be concerned any tips welcomed.  I am learning CC Automation and just trying to assign the Dynamics knob of 8 Dio Adagietto causes Audio dropout anybody know why? Oh yeah I amlost forgot I have my projects saved on a different drive Platinum gave me a nasty gram saying project was invalid, I manually open the project from my D drive will this be a problem going forward?  Not feeling that warm an fuzzy at the moment

Kontakt 5 has been working great for me in SPlat, but I don't have any full 8 Dio libraries.   Do the libraries included with Kontakt seem to work OK for you? 
 
I would also double-check your drive situation - if the same project loads correctly from one drive but not the other I'm not sure how or if SONAR itself might factor in.   Plus, I'd imagine most do use a separate driver for projects.  What is that drive that you're using?
 

My projects are on my D drive and Platinum wants them on the C drive

Did you go through and setup the file preferences in Platinum? Platinum works like every previous version WRT file preference settings.

John

Fabio Rubato
Well, I was excited...until I tried to install it and received a blue screen because of some conflict with bdfsfltr - which appears to be a part of my virus connection. So I could only install it in Safe Mode. Even then, Plt continues to crash and stop working - apparently it doesn't like Melodyne or at times my Roland Quad drivers - but also for other 'unknown' issues. So now, if I want to update, it has to be via Safe Mode - even disabling virus still gets me a nice blue screen. 
 
It's slow to open projects as well and really apart from midi manipulation improvements and the rematrix solo, there's not much in it for me. X3e continues to be my 'go to' DAW as it rarely if at all crashes and loads projects quickly.
 
If I had to do it over again, I'd probably just try the monthly payment option, as by now, I would have cancelled it...just sits on my system now as I won't touch it anymore...rather spend my time making music than stuffing around with Plt. Big waste of time and money for me.
 
Just my experience of it. So I'm not going to try to convince you to upgrade. I would advise you rather to try the monthly option if it's still available;

It seems to me that your virus setup is the problem. Most people use MS essentials or some non conflicting protection. Some do without and have their machines offline. I suppose what is a priority to you is not one I have. I much rather be able to run my programs without trouble. But thats just me.  

I've followed this through and uninstalled IOBit malware and 'advanced system care' and installed MEssentials...and that did the trick. Updates via CC working now without that dreaded BSOD. Thanks heaps for the suggestion...now if only Melodyne VST will update to the 2.1.2 version...one step at a time I suppose.

2 out of 3 replies above seem to be from Cakewalk folks and or 'volunteer moderators', whatever dubious position they hold.  
 
But as a general critic of Sonar, upgrading to Platinum from x3 seems to have been good.   Few improvements of the things that matter to me (GUI, PRV, EL) but nothing made worse.    EXCEPT FOR THE COMMAND CENTER!!! beware about un-knowing install to your C drive, if that is not where you want the installation.   READ about it first.