I have the same basic system you have only mine has 2 gig of ram and the 7200rpm drive. I have had it for about 2 years now and have NEVER had any of the problems that you are having so i would have to say it sounds like you got a lemon.

As for the heat part, yes they do run rather warm, but that can be helped by using the fan control program. I don't know what your expectations were when you bought your system, but you might remember that Apple is not heaven and Jobs is not God. Now and then a lemon slips off the line, take it back to Apple and see if they will make it good.