Hi - Since installing AFX CC 2015 this error (image below) has been popping up more often than not.
I believe its related to running to running 8 bit plugins in 16 bit projects. It never was an issue for me prior to 2015 release. But the most annoying thing is it essentially gets you caught in a loop where you can't exit out of the error. AFX itself doesn't crash but the error box won't go away.
The only way to rescue a project if you haven't saved is to keep clicking the OK button until you see an autobackup save occur inbetween clicks. I'm not sure what to ask but .... why Adobe why?
I'd add it to the list of the many issues with the new rendering pipeline. Perhaps you should seriously consider reinstalling CC 2014. Otherwise of course try to update your plug-ins, if that's possible.
Have you installed any third-party plugins? They need to be updated to work with CC 2015 plug-ins and After Effects CC 2015 (13.5) | After Effects region of interest
If there are no third-party plugins, file a bug report.