weird ibook problems

Hi there, maybe you can help me out

sometimes, i dont know what might lead to this, my iBook wont let me volume up or on with a weird signal that shows a crossed out speaker symbol, obnnly thing helping when this happens is reebooting.

what could be the reason to that? and how can I avoid it without rebooting D:

btw.: iBook G4 with Leopard latest update

nope its just does it out of the blue

always all the time after I had it o sleep mode while changing rooms in University or to sace battery while on a plane

I really dont like to reinstall leopard because it tkes so long, sof if someone knows a work arround, I would be happy ^^;