Ok, the command line to star mozilla in mozilla.
Try running the command (not from a V terminal) using [alt] + [F2] and typing mozilla. if it still doesn't work try running it as another user (or maybe root, not very secure). Check if the link is working (in the properties make sure that the path is corret).
Make sure she didn't modify her env. try adding /usr/bin to the PATH variable
[user@domain user]$ PATH=/usr:/X11R6/bin:/usr/local/bin:/bin:/usr/bin
[user@domain user]$ export PATH
You could try using another WM like KDE, perhaps it would work.
do you get any error when you start it from a console (or Virtual Teminal)try running
[user@domain user]$ /usr/bin/mozilla
If that does not work try explaining better your problem.