I was working a project yesterday when this error appeared. I went through various fixes I found online (rebuild Dbs, delete MCstate, create new user and maybe others I've forgotten...) None of them seemed to help.
Here's an example of what happens.
I can open the project, however, the "unsupported" dialogue box does appear. I dismiss it. I load an older sequence. It plays fine. I make a duplicate and begin to work on it. Now, if I try to do anything other than edit the audio 1 track, I immediately start getting the error and the sequence won't play. Even if all I do is delete a couple of upper tracks (I was trying to troubleshoot if there was a bad clip...) the error appears.