Heat shouldn't REALLY bother P4's because don't they slow down enough to keep them from burning up? Tom's Hardware did a little think on that, and they didn't burn up without a HS, unlike the AMDs ;P
But yeah, something's wrong here... I wouldn't think it would get this high, but do you think you have too much termal grease? That can cause a problem... Why not get some high dollar stuff, clean up your processor and HS, then reapply just a bit... Just a dab on your finger and lightly coating the die is all you need... I redid the processor on my laptop and it runs a few degress cooler now!
I SERIOUSLY doubt a ground would be a problem, but it would be a good idea to screw them all down just to be sure everything is grounded proporly and the mobo is not being bowed...