firefox crash viewing video on CentOS 5.5

Firefox / seamonkey crash on CentOS 5.5 (we use x86_64, haven't tried 
i386) when they encounter non-flash video files, e.g., 
http://www.nist.gov/itl/math/hpcvg/upload/vaneRheom_20101203_02.wmv  or 
other videos at, for example, 
<http://www.nist.gov/itl/math/hpcvg/concretemm.cfm>.  I've also tested 
some other .avi's with no success.

This started happening about 6-8 weeks ago.  mplayer from the command 
line plays the videos fine.

Can't quite put my finger on if it's gecko-mediaplayer or gmplayer.

I've got a bunch of debuginfo's installed, probably not all the needed 
ones, but note that 
http://dl.atrpms.net/debug/el5-x86_64/atrpms/stable/mplayer-debuginfo-1.0-78_snap20101002.el5.x86_64.rpm 
is only 10KB in size and 'rpm -ql' reports no files.

gmplayer (part of mplayer package) dies on startup too.  Looks like a 
smoking gun to me.

Anyone out there view non-flash video anymore?