Sound Problem

hi,
On an eMac G4.
I am having the wierdest problem. My sound has gone off. I have tried using only headphones to see whether its a speaker problem. It still doesnt work. And, i checked. Its not on mute.

I also had it working for some time,when i had rebooted. Nows its fallen silent again. Any ideas?

thanks

try starting up wour mac while holding shift to boot without extensions, if it works, something you installed recently(hardware or sofware) is causing an extension conflict.
do you hear the mac 'chime' when its starting up?