Lost my Gnome/Mate gui

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http://forums.fedoraforum.org – I installed Mate in my F17 system to check it out. Seems fine, but of course I ended up with lots of 'duplicate' applets in the menu. So, one by one I started to clean up the extra entries. After a significant number of PackageKit sessions, I felt that it was mostly done. So I rebooted the system, but the primary session does not startup with the gui interface, just gives a blank screen. I can get to the other tty sessions and log on in text mode, but I do need to get the gui back. The assumption is that I removed one or more key packages during the cleanup. So, how can I figure out what tho (HowTos)