I've been having this problems for several months. My newly built computer will turn on but won't get past the boot screen and it won't recognize the mouse now. I tried changing out the motherboard and it wouldn't even start up. Just the fans would turn on and then it would turn off. I took everything out and rebuilt the whole thing and it was able to start up and I was able to install Fedora 14 on there but when I shut it down and tried to restart it today it wouldn't work. There are 4 lights (one being red) on the motherboard at all times now which looks like the cpu is not loading.
-NZXT Apollo Black SECC Steel Chassis ATX Mid Tower Computer Case
-gigabyte p55-ud3l motherboard
-4 GB of DDR3 memory
-i7 860 CPU
-HIS Radeon HD 4670 graphics card
-1.5 TB Sata Seagate HD
-Corsair TX850W Power Supply
Just tried to start it up again and I'm getting 4 phase lights (2 green, 1 yellow, and 1 red) which is suppose to indicate the CPU is loading but then they just stay on. Also now it will recognize the keyboard but not the mouse and it still gets to the motherboard boot screen and stops.