ya i had this problem as well on a old motherboard with 3 dimms.
the 256mb stick has to go in dimm1, the 512mb sticks have to go in dimms 2 and 3, then it will work. dimm 2 and 3 have to be matched pairs.
i downloaded it and installed it. and its amazing. much better then Beta 1, so much faster and it doesn't crash. the live preview thing in power point is very nice. ill add more once i have some time to play with it somemore.
its nothing with heat, i had the exact same thing happen on my Dell Insprion 8200 a few times. for me it turned out that it was a problem with the driver for the touch pad. but to get it working normal, i had to format and start over again.