We use current production (not beta / pre-release) releases of x86-64 
Linux Mozilla Firefox (as well as Mozilla Thunderbird), not the distro 
ESR version.  There are a number of reasons for this that can be 
discussed under separate cover.  The environment is SL7x.

Firefox often (almost always) fails to open, with the diagnostic:

[ykarant@localhost ~]$ /usr/lib64/firefox/firefox
XPCOMGlueLoad error for file /usr/lib64/firefox/libxul.so:
libmozgtk.so: cannot open shared object file: No such file or directory
Couldn't load XPCOM.

A simple script "fixes" the problem.  I keep the run directory 
/usr/lib64/firefox that has the installed compressed tarball files 
duplicated in /usr/lib/firefox-current , and then as root superuser rm 
-rf the run directory followed by a directory copy of the duplicate 
directory into a new copy of the run directory.

Does anyone know what causes current standard production firefox from 
"destroying"
/usr/lib64/firefox/libxul.so ?

Yasha Karant