@zeflash
You could be running out of video memory? Check my earlier post.
Kind of a hunch here...
Who of those experiencing the issue is using the TVSeries plugin at all?
Tourettes, are you using it?
I've did some tests this afternoon after a reboot - starting a movie from movingpicture or myvideo doesn't seem to adversely affect the framerate of the animations, but starting a show from TVSeries seems to do something wrong.
I'll try to compare how all the plugins are starting a video. I didn't do the video playback code in TVSeries - not pointing fingers toward anyone, it's just that I have no idea what could be different and/or badly done in TVSeries to trigger this issue.