Comment 9 for bug 518873

I am also having this problem. Here are some relevant details:

Problem system: Ubuntu 9.10 amd64 (nvidia drivers from ubuntu repo)
Unproblematic system: Ubuntu 8.10 x86 (32-bit) (nvidia drivers from ubuntu repo)
Both running roughly the same apps.

Problem: Periodically on boot the menubars are blank (both top and bottom although System Monitor applet is still working in the bottom one) and sticky notes are not displayed. Desktop background and icons are in place as usual.

Solution: killing the gnome-panel process (although the weather applet is missing from the menubar after it restarts).

Let me know if there is anything else I can do to help with this. It recurs periodically (4 - 5 times since 9.10 install) and I think this would effect newer users a lot more since there is no way to shutdown properly or restore it without help (rebooting does not fix the issue). Hope this helps,