So I have a 17" Flatscreen 1ghz iMac that has worked great up until now. It is up to date with 10.3.9. I have not changed any settings or installed any new software recently. Here is my problem: The iMac's screen goes dark randomly (approx. 5-30 minute range- sometimes longer). When this occurs, the iMac is still running (fan and screen noises can be heard still) but the screen won't "wake up" from dark. I have checked energy saving, monitors, and security preferences for any check boxes that would explain my problem- but no luck. What could be causing this? Screen going bad? Software issue? Ideas? additonal info: Under Security preferences the box that reads "log out after __ minutes of inactivity" has been checking itself on occasion. I never have checked this myself (and I am the only one using my computer) but randomly over the last several months this box becomes checked. Weird!