Even if you had put too much (or even too little) paste it just shouldn't be heating up that quickly to that level. Are you sure the retention mechanism is engaged properly? I've also got to ask... did you remove the little thin piece of plastic that typically comes on the under-side of a heatsink? I totally goofed on my current build... I knew the plastic was there... I read the label that said REMOVE BEFORE INSTALLATION... and it just slipped my mind. Mercifully I caught this before I tried to do anything with my rig, but I can only assume that piece of plastic would have really jacked with my temps.