[CentOS] Centos 5.8: starting firefox-16.0.1 kills X

This just started happening this evening.

a little history:
way back last year, or thereabouts, I posted about a weird problem I was
having. over the course of 2 or 3 days I figured out how to fix it, but
not what the cause was. the fix amounts to navigating to my user's 
.local/share/mime directory and removing the file named "globs".

So, back in the present: this evening that same problem recurred for
the 3rd or 4th time since the original event mentioned above. so I
deleted that file, logged off and back on (without the log off/on, the
problem still occurs).

Having done that, I went to fire up firefox and KABOOM!!
X dies and I land back at a login prompt. 
several times. 
every time.
tried running firefox from a terminal but I don't see anything
echoed to the terminal before it is blown away.

I still have the tarball from mozilla.org, so I moved aside the directory
where the firefox runtime stuff is, re-extracted the tarball and it still
croaks in the same way.

I'd appreciate some ideas to try, if anyone has any. Thanks in advance!

In the meantime, Opera works (though I can't install 12.0.2 for lack
of a suitable version of rpmlib, so I'm not left browseerless.

Fred
-- 
---- Fred Smith -- fredex at fcshome.stoneham.ma.us -----------------------------
    "Not everyone who says to me, 'Lord, Lord,' will enter the kingdom of
     heaven, but only he who does the will of my Father who is in heaven."
------------------------------ Matthew 7:21 (niv) -----------------------------