Similar problem here with a mid-2010 macbook pro 15". Makes my blood boil!
Had the three beeps, kernel panic, screen roll-down telling me the computer needed reboot etc - even completely dead with only the light going on but no other response whatsoever. All this happened at random and in between the computer was running just fine.
Switched the RAM around and it worked!.... for a while...then I ran on just one 2GB ram and tried it in both slots and it was fine for several days - so I figured it was the other RAM that had gone bad. Got two new 2x4GB and tried them - worked fine for 2 days and then I was back at square 1....
Lesson: Before getting new RAM, try both RAMs individually in both slots over 4-5 days and then see if its a faulty RAM or a faulty slot. For me its the lower slot. Running on a 1x4GB in the upper slot now.
So - slots can go bad on a Macbook Pro. Hope this prevents someone else from making a mistake.
Cheers! /J