I recently noticed my MBP (7.1, 2.4GHz, 4gb) behaving sluggishly then it started not wanting to wake from sleep mode. I usually have no problem closing the lid and re-opening it. It started not wanting to wake up, forcing me to perform a hard reset. I then checked to see if anything was a miss, and it was saying that one of the slots was empty (2gb was missing). Resent the PRAM, everything is fine. Still having sleep problems and everytime I do a hard reset it boots with an empty slot. I initially thought this was a Lion issue, so I restored my computer back to snow leopard and updated it back to 10.6.8. Problem is still there. Memtest says everything is fine, both with only 2gb showing and with 4gb showing. I have read a bunch of different threads all over the place and no one really has a solution. I just want to see if anyone has been having this problem with Snow Leopard, as most seem to have it with Lion. Even found a couple people having the same sleep issue with ML. It's really driving me nuts.