Yesterday I changed my panels to be transparent. I'm running up to date rawhide with nv graphics and metacity in composite mode. Yesterday when I changed them to transparent, things worked fine. But when I logged back in this morning, the panels were there but invisible. I could mouse over panel items and get tooltips. Running gconf and unchecking composite manager made them reappear. Rechecking composite and everything was still fine. metacity-2.21.5-2.fc9.i386 xorg-x11-drv-nv-2.1.6-7.fc9.i386 I do have the XAANoOffscreenPixmaps option of the NV driver enabled which fixed a problem with transparent gnome terminals.
I've logged in twice today and it worked fine. Closing for now.