A note to all the Pandora users; Pandora does work in FireFox 1.5 [Edit: this fix also worked on my 1.0.7 install], but it may not work perfectly if you have the Adblock extension installed.
Symptom - Pandora loads, and you hear music, but you don't see anything.
Possible fix - Go to Tools->AdBlock->Preferences, click on the AdBlock Options button and make sure that "Obj-Tabs" is un-checked.
Another one I ran into was this;
Symptom - The Pandora page loads, but the player never appears and no music plays.
Possible Fix - Reinstall Flash. You'll need to get the proper uninstaller from Macromedia (I used these). Close and relaunch FireFox, and reinstall the flash plug-in.