This is unlikely to be a bug in C2 as there would have been lots and lots of people posting about it. I for one have no issues exporting from r170, which doesn't mean it isn't C2 at fault for you, just unlikely.
When did this start occurring? Was it after an OS or GPU update?
What doe Windows Event Viewer say (if anything)?
Have you got Java installed (for minify)? What version?
Have you tried exporting without minify or PNG recompression?