On of the options I really like in Gnome, is the possibility to save your current session at logout (found under system > preferences > sessions : session options).
I've been using this option ever since I discovered it in Ubuntu. Very usefull if you have six desktops with lots of terminals and other windows open and want to resume everything after a restart. However, during the past weeks, I experience more an more problems with saved sessions which are totally broken. Today a broken shutdown button got saved into my session, I could click the shutdown icon in the menu or on the taskbar, but nothing happened. No idea how that can happen... Few days ago the session was saved without a running gnome-panel, so no task bars at all once you login. That's annoying and can certainly be a problem for less experienced users. It's probably not that easy to detect such a problem when the session is saved, so the user should be warned to use it carefully. :-)
If your session is saved in a broken state, erase it by removing $HOME/.gnome2/session and login again (make sure you're not logged in in Gnome and/or have save session disabled when you remove the file).