Cakewalk shutting down sometimes

That's a tough one, because that particular exception is not raised by the module that actually triggered the fault. Your best bet is to send a copy of the minidump to Cakewalk for analysis.

http://www.cakewalk.com/Support/Knowledge-Base/2007013262/How-to-collect-a-Minidump-file-when-your-Cakewalk-program-crashes
 
A minidump is a file that SONAR creates when it crashes. The file contains essential information about the state of SONAR at the time of the crash. The Cakewalk support folks can then analyze this data to perform a sort of post-mortem autopsy and hopefully deduce the cause of the crash. 

It is a Microsoft error. I did a quick google and it seems to be related to 32bit apps running on a 64bit machine. The atrticle that I saw recommended checking that you have all the latest Microsoft hotfixes.Specificlly here is the error code:

Exception code: C015000F The activation context being deactivated is not the
most recently activated one.
 

It would depend on what you installed. A 64 bit OS can run 32 bit programs. If you installed the 32 bit version it could be one cause. It more likely a 32 bit plugin. 

Polly13
OK. Do you know if Sinitus is 32 or 64?

Its both. If you run 64 bit Sonar most of the CW plugins will also be 64 bit. With 32 bit Sonar there are a handful that are 32 bit only. These are very old DX plugins and are not ported to 64 bit. Most have been. 
 
You can check which Sonar version by going to help and about. It will list the version and bit depth.