the only way to freeze matroska is the sequent :
If you have an avi with duration 5 min
Audiostream 1 (ex ac3) duration 2 min
Audiostream 2 (ex ac3) duration 5 min
Then if you go to 3rd min (using the seeking bar) the bsplayer freeze the movie.
If you decide to do to 1st min then plays again .
Also try to uninstall / reinstall the ac3filters . Use these filters :
http://ac3filter.sf.net