My screen will freeze, but the mouse cursor can still move, but can't click on anything. Have to use the hard button to turn off Mac. Then it comes up to the login screen but mouse still won't work. Usually if turn off again and then return it on the second time around the mouse will be able to click on a login and it will go into the OS. It will work sometimes for an hour, sometimes several hours and sometimes only a short time. First I tried reseating my ram, didn't work, then I checked each one individually and still ended up freezing with each one. Then I took my old ram, which was good and it still froze up. The newer ram is over a year old, so it wouldn't be from installing new ram. Occasionally when starting up, I will hear one long beep, but it will go to the login screen or startup the OS even though it beeps. Any suggestions? I have an iMac 2.8 GHz Intel Core 2 Duo with 4 GB of 667 MHz DDR2 SDRAM. I'm wondering if this is some kind of hardware issue because of the beep. If this may be something else, can you direct me to the appropriate forum. Thanks.