First problem: Was reaching the end of an animation and after clicking test movie, it only launched a small blank box instead of the movie. It still exported the .swf file, but I can't test it on flash. It then wouldn't export as a .mov at all, with the error message 'could not complete operation due to unknown error'.
After closing and opening again, I was able to test in flash and even export as .mov. However on the first try it was about half the height for some reason despite being set as 950x550, and on the second try it was just white. Having tried to export it a third time it's working, but still half the height and squashed.
Looking at similar threads I think something in the library might be corrupted, however I deleted everything that I imported since it stopped working and that made no difference. Is there some way of finding bugged files to be sure? Or is it something else I'm completely missing?