No need for all that I'm sure you did a fine job, although its worth a shot if you think it might have went on funny or you used to much paste. Just don't mix two different kinds if you re-apply, clean first then apply the new stuff.
It's more simple science really, you bought a 400 gram heatsink. You figure sandy is 95 watts at load and OC'd a good bit over 100 watts. 400gram sinks are only rated for about 120 to 140 watts so you're already pushing the limits of the cooler at stock. The closer you get to max potential of the sink the less capable it is of staying cooler than the CPU and temps start to creep up. If you'd spent $50 bucks instead of $25 you'd of got an 800 gram sink with significantly more surface area and a dissipation closer to 300 watts which will dramatically reduce your temps at load.