Re: Mplayer - vdpau - composite disabled screen flashing
The VDPAU debug log (if any) would appear on stdout/stderr of MPlayer; it's quite possible there was none in this case.
I don't see anything in the logs nor the bug report file to indicate what's going on. I assume this was using your TV out (i.e. not DVI), where you just get flashing, but not black screens and X hangs? Is it possible for you to repeat the process using DVI (run MPlayer and the bug report script over an ssh session) It's possible that this will generate different error messages in the bug report file.
Finally, could you take a short video of the flashing and post a link to it?