Cannot write file, disk may be full (Redux)

I haven't seen this one since SONAR 5 or 6, but I was opening several old projects the other day, doing some tweaking and exporting, and it happened twice (2 different projects).
 
The usual symptoms when it happens-  You can't save the project even on another physical disk.  If you cancel SONAR crashes.  As an extra bonus the autosave file is "truncated" and can't be opened after restarting SONAR.
 
Checked the disk, it's fine.  I've seen lots of threads on this over the years, but have never seen any reliable way to make sure it doesn't happen. 
 
Has anyone else seen this in X2a?  Anybody know how to prevent it or recover from it?
 
Thanks,
 
John

carl


John, 

This may not be very helpful but when any Sonar version project will not save or starts acting flaky I first start off by deleting all the files in Picture Cache folder. Next I check plugins or the audio files in the project.

Hope you find a fix.

Thanks, Carl, I didn't try deleting the picture cache files, but worth a try if it happens again.  I'm wondering if it only happens on projects created in older versions of SONAR, since that's the only time I've seen it in X2a.  Of course I have a limited sample size, so it may just be coincidence. 
 
It could be (and probably is) related to older plugs in the older projects, but once the problem happens even deleting the plugs doesn't seem to help.
 
John