I have a bad memory slot
I'm working on a MacBook Pro 13" 2.4GHz (Mid-2010) that has a beep every 5 seconds. After a bit of troubleshooting I found that the top memory slot is bad. The MacBook works fine with each 2GB memory module (installed one at a time) in the bottom slot. Anything installed in the top slot causes the beeping error. I have tried cleaning the pins of the slot with Isopropyl Alcohol and compressed air. Instead of replacing the Mother Board, I thought why not just run it with memory only in the bottom memory slot and instead of only 2GB, put in a 4GB module. It won't boot with the 4GB module installed. It hangs on the spinning sprocket. Normally, nobody would run a MacBook on a 0+4 configuration, but has anybody tried? I either have a bad memory stick or it's not possible. It runs fine in a 0+2 configuration.
Are you sure you have the correct SIMMs for this system? are the SIMM's you have the same brand, spec and I/O speed (2GB SIMMs). If not your SIMM's may indeed be the issue not the socket.
Mixing different sized SIMM's can be tricky as the smaller sized SIMM needs to be in a given slot. But before you go into adding this 4GB SIMM make sure its I/O speed and specs are correct for this system.
Review your models memory requirements from Apples Tech Note: http://support.apple.com/kb/HT1270
The first slot (slot 0) needs to hold the smaller SIMM if you mix sizes. Running different sizes forces the computer into a slower I/O method. If you use the same size (matched set) your system will use inter-leaved I/O which is much faster!
I would try a fresh set of matched SIMMs (2 or 4GB) to make sure your going down the right path here.
In any case using the wrong type and speed of SIMM or you have a mis-matched set can create sporadic operation and cause the reaction you are seeing.
You know? I have the same issue on my early 2011 15" mbp that is spec'd out.
I didn't get Applecare and i don't feel like laying down for $900 logic board replacement with apple. So, this is the 'solution' i've thought of. I haven't tried the 4 GB in one slot yet. Just rocking the 0+2 GB config just like you.
i'm wondering what could make my macbook act in such a way. it's bizzare.
Mine isn't the top slot, my mbp has the bottom slot that is the issue.
I did the swap/test/test/
I'm going to the Apple Store to see what they tell me tomorrow.