Firefox v3 and CIFS Home-Dirs
Firefox v3 uses SQLite internally — for saving various bits and pieces under ~/.mozilla/firefox/<string>.default. If you home-directory happens to be a CIFs mount, you may well experience problems: Firefox v3 will launch fine, but refuse to load any URLs. Poking around in ~/.mozilla/firefox/<string>.default you will see lots of files like places.sqlite...corrupt.
Shutdown Firefox; remount your home-dir with the nobrl option — see the mount.cifs man page for details, for example, from my pam_mount.conf.xml
<volume user="mpciish2" fstype="cifs" server="vdm02-g1.ds.man.ac.uk" path="HOME"
mountpoint="/home/mpciish2" options="nobrl" />
and all should be bubbly.