USB Ports Not Working

[Malky]

I recently went away for the weekend and when I came back my USB ports don't work. When I first start my 24" iMac the mouse lights up but then goes off later on when it's booting up. I really don't know what to do and i'm not even sure if I got any discs with my iMac as it had Leopard preloaded...

 

[Malky]

C'mon guys I really need urgent help, please?

 

[rdowns]

Try resetting the PMU. Follow instructions for your model.

http://support.apple.com/kb/HT1431