I might have fixed the problem.
Maybe.
I was having problems with YouTube videos too with the videos ending early prior to how long the video says it is.
I read the YouTube help Google thing and found the problem and it said "Enable JavaScript"
Now... I had JavaScript disabled for a LONG time due to the security issues they've been having.
I re-enabled my Java FireFox plugin and it seems to have fixed the problem.
I haven't truly tested it but maybe this has worked.
If not I guess I wait for another flash update and hope the update fixes the problem.