A week or two ago my Mac just restarted on its own twice and was then running slower than I've ever seen it run. I checked the system preferences and it listed only 2GB of RAM [I had 4]. I have a red light on DIMM 1 on my lower riser card so I thought it might be the ram. I bought another 4 GB of ram... same problem. I tried different orders a single pair (new ram only), double pair, I tried everything. With two pair (2x4) in it would read 4GB but says the lower card is empty. I went ahead and bought another riser card to replace the lower one with the red light on it... same problem. Please tell me it's not the logic board and I'm missing something. I can't afford $800 to replace the logic board.