That's the problem with installing a DE over something else not designed for (I constantly do it anyways
). Their may be tweaks/hacks to better the default DE in the system But
may have adverse/unintended results in other DE's. (Hence the problems nautilus ect. have on XFCE in both LMDE and LMint 12 when XFCE overlayed onto.
The only solution (I can think of) is to make sure not running thunar and *nautilus also
*(check in task manager) kill if are, and resave session, then make sure not restarted in auto start and unclick save session in log-out screen.
P.S. if not going to use Gnome also may want to get rid of nautilus (purge) in synaptic.
If none of that works I'm at out of ammo (and I put (at least try
to put XFCE on everything)