I had the same problem - it is user based.
Drop to a terminal and move into the (normally hidden) .mplayer directory with cd .mplayer
Check the dates and times of the files by an ls -al
. Below is mine - note the date on the config file - it was when the video disappeared for me:
drwxrwxr-x 2 roger roger 4096 Jan 25 2009 .
drwx--x--x. 153 roger roger 20480 Oct 27 23:22 ..
-rw-rw-r-- 1 roger roger 44 Jan 25 2009 config
-rw-rw-r-- 1 roger roger 2881 Oct 27 23:22 gui.conf
-rw-rw-r-- 1 roger roger 70 Oct 27 23:22 gui.history
-rw-rw-r-- 1 roger roger 36 Oct 27 23:22 gui.pl
-rw-rw-r-- 1 roger roger 838 Oct 27 23:22 gui.url
To fix it, simply delete the config file with: rm config
Try Mplayer and you should have video back.