mplayer 1.0rc2, specifically, it's the mplayer from debian-multimedia.org
I simply run mplayer -vo caca file.avi
However, I've just tested it using xcompmgr again, and I cannot reproduce the crash/lockup anymore. Instead, when I hit 'q' to quit mplayer, xcompmgr prints these:
error 3 request 20 minor 0 serial 40922
error 3 request 20 minor 0 serial 53494
(one line for each quit)
Perhaps 169 somehow fixes the issue with xcompmgr.
Now I can only only reproduce the issue under compiz.
Thanks for looking into this.