Everything was fine. Then I ran the software update and there was Safari 4.0.5 and I decided to update. After my iMac had restarted, the OS went complitely berserk. If I click the dropdown menus, they start to flicker and run trough over and over again by itself and I can´t click anything. My mouse buttons do straight things, bring up the finder and then I can´t even go through the folders. I can´t write with my keyboard, it just gives me random letters and I can´t delete them. I mean the computer went complitely crazy. I´ve never seen anything like this and I´ve used this iMac perfectly now almost two years. Everything is just flashing, flickering, jamming, cursor disapperaring and doing straight things, I can´t do pretty much anything. This has to be a virus, right? Please help!