I too am having speaker problems or sound problems. Everything works fine with 9.0.4 & 9.1, however no modem sound or no Pele Speakers working for now. I hope someone figures these out. On my Rev. D iMac 333.
I too have had this problem with the PB on a 333 iMac, I was hoping it would have been fixed by the final, as I have sent in a bug report about it. However no luck, Final does the same thing.
I have ended up plugging my speakers into the headphone jacks at the front (the internal speakers suck on the rev. d).
One thing to remember tho, you have to unplug and plugin again the speakers after a restart or login, otherwise no sound. I'm not sure if you have to have something making a sound when you do this or not. I usually forget until I play iTunes, then just yank the plug in and out quickly.
This behaviour is really weird, I have only heard of it on rev. d's. Has anyone else had this problem of other machines?