I have the same problem, but still no luck on finding a solution. I started having this freezes like a month ago, I had 2x4GB crucial RAM sticks. Read online that it may be a RAM problem so I switched back in the old 2x2GB apple RAM, but I still get the freezes and the beeps.
There are times that the mac simply refuses to boot. When this happen I boot from the windows bootcamp partition and everything goes fine.
Heat issue? maybe. After I cleaned the dusty fan the computer lasts longer.