I am currently trying to put together my first pc and am having trouble getting my pc to boot. When everything is in the case and plugged together the LED displays "FF" right upon start, and it remains stuck on the FF indefinitely.  I also get no display on my monitor. After reading several posts from other people, this either meant a grounding issue or a bad mobo. The way to test was to take everything out of the case (PLACE on cardboard) and plug in only 1 gpu and 1 stick of ram.
When I did this, the motherboard BOOTED just fine. I am now wondering what I am doing WRONG when putting everything in the case. I am looking for ideas to try and things that an amateur might overlook. Any help would be greatly appreciated.

Specs:
Motherboard: EVGA 132-CK-NF78-A1 LGA 775 NVIDIA nForce 780i SLI
CPU: Intel Q9450
CPU cooler: ZEROtherm BTF90 92mm Silent UFO
RAM: CORSAIR XMS2 DHX 4GB (2 x 2GB) 240-Pin DDR2 SDRAM DDR2 800 (PC2 6400)
HD: Western Digital VelociRaptor WD3000GLFS 300GB 10000 RPM
GPU: (2) EVGA 512-P3-N841-AR GeForce 8800GTS (G92) 512MB 256-bit GDDR3
Case: Antec 900
PSU: SILVERSTONE SST-ST75ZF 750W ATX 12V 2.2 & EPS12Vdid you put standoffs in?Yes, I put standoffs in wherever there was a hole in the motherboard for them.only on the holes with metal around them too right?