off-topic: use care with centos/rhel 5.6. this is Fedora6/legacy material (read: obsolete). SL6.1 is far more fun.
not that familiar with VM stuff, but is nautilus in its list as an application? IIRC, nautilus is (pre3.0)gnome-specific, and virtual environments used to be home-built and it's configuration seperate. do you have a .config file present you can caress? contestants welcome to jump in.