I'm not sure if there's already a thread on this, please excuse me if there is. Most times my iMac 7.1 starts up fine, but once startup is completed, I find that my USB ports don't appear to be working (USB mouse doesn't move, keyboard isn't responsive, any USB flash drives are not detected). I restart using the power button and on the second startup, everything is fine. Can anyone tell me any way I can solve this problem? Is there reason for worry?