Thunderbird won't "Compose" new or reply message

[Douglas Phillipson]

I just installed FC6 on a Dual Athlon box.  First I had the "udev"
problem where it would hang on the modprobe line in 50-udev.rules, which
I commented out so the system would boot.  Then the GUI to create a
xorg.conf for multiple monitors wouldn't work, it never does for me.  I
manually configured it and Xinerama on 4 monitors now works fine.  

Lastly, Thundirbird won't allow me to compose or reply to a message.  I
get the error:

An error occurred while creating a message compose window. Please check
your installation.

I've never seen this problem before.  All other popups in Thundirbird
work ok from the tools menu.  It's a strange one!  It works ok on FC6 on
other computers but not my Dual Athlon box.  This was a fresh install of
FC6 on what was an FC4 box.  My home dir remained intact.  Couls there
be a FC4 setting in my home dir messing up thunderbird?

Thanks

Doug P