My copy of Flash stoped letting me import files?

Hello all, got a bit of a weird problem.

Just yesterday dragged and dropped a .mov file into Macromedia Flash 8 and like always I got a sequence of usable bitmaps, but after fully tracing and editing it I went to drop another .mov file and nothing happened. I tried to import it and Flash said it was an unsupported file/format, it even said this when I tried to import .mov files I had previously imported. I'm not sure what could have change in a mater of hours, but I can't make an use of my library of effects at the moment. Is there a way to reset whatever's gone wrong?

I have had this issue. I don't know how i came to a conclusion. Hope someone helps you in a better way.

Thanks for your helpful information. I have been struggling to find many questions about this issue.