fans going, screen flickering...

Mike,

You can try doing a SMC reset and/or you can contact AppleCare, the phone number is in your owners manual. If you have never done an SMC reset here are instructions




_SMC RESET_

• Shut down the computer.
• Unplug the computer's power cord and all peripherals.
• Press and hold the power button for 5 seconds.
• Release the power button.
• Attach the computers power cable.
• Press the power button to turn on the computer.





_PRAM RESET_

• Shut down the computer.
• Locate the following keys on the keyboard: Command, Option, P, and R. You will need to hold these keys down simultaneously in step 4.
• Turn on the computer.
• Press and hold the Command-Option-P-R keys. You must press this key combination before the gray screen appears.
• Hold the keys down until the computer restarts and you hear the startup sound for the second time.




Roger

Michael I had the same thing happen to me last night while compressing video followed by a defrag of my hard drive. Did your problem get fixed ding the SMC and PRAM resets?

It doesn't hurt to do the SMC reset. BTW why are you defraying your HD?

I've had not trouble since last week, but I haven't really used the iMac hard and the weather has been cool. In other words I have not been using it the same way I was when the screen went wonky.

I will give the resets a try. As for defragging the hard drive I do that once a year. My HD was 32% fragmented. Thanks for the help.