Mint 12 login with Gnome has no menus/ title bar

[hulinux]

Hi all, first post ever here, new to Linux mint (Lisa 32bit no codecs download to cd and installed on new partition by windows 7 on C:) a few weeks now. Generally love it, no problems until today (except it could not detect my canon Lide 100 scanner). However, today while working with rdesktop and firefox running machine froze, I had to hold down power key to turn off and reboot, but when rebooted as normal the desktop screen has no menus, just my home and computer folders. Only way to get proper use I found out is to log in and change to Gnome Classic. Coincidentally, yesterday I discovered the settings for themes and had a play around with them, but problems only happened today. I hope there is a simple solution as I really had gotten used to and preferred the Gnome desktop.
Thanks for any help

[jerkins]

I would also be interested in an answer to this problem: I have just installed Mint 12 - Gnome Classic works as expected, but the standard Gnome just shows the Computer and Home icons, plus Thunderbird (which is set to autostart at login).

The top and bottom panels are missing.

UPDATE:

I don't have any "Shell Extensions" listed in the "Advanced Settings" application.

FURTHER UPDATE:

I've lost interest - I've gone to Mint 12 KDE, which just works...