iMac -- Sound locks up

[macgeek77]

I have an iMac G5 iSight and I installed Leopard on it the day it came out. However, in the past week, I have noticed that my sound locks up. By locks up, I mean when I adjust the sound on my keyboard, a little circle with a slash through it shows up under the dots representing level of sound (wow I made that complicated). Also, a song in iTunes won't play when it is like this. I often have to restart and it works. Could this be a problem from the 10.5.1 update? Thanks for any help!

 

[mad jew]

Do you have any hardware plugged in at the time?