I believe this is a bit of a catch-all error were something else goes bad but that error isn’t caught which causes THIS to go bad, where the error is caught.
Are you still using the 50MB upload volume size? It should’t be needed (I know some people have gone up to 1GB) but it seemed to resolve the issue for you last time…
In the past, it sounded like one of the sources of this error was a “dinosaur” file - though this should have been fixed long before 2.0.3.3 beta… though it’s possible this specific bug snuck back in…