CPU Hits 80c playing flash games

Here's the deal. I've got a Pentium 4 3.2, not overclocked. I noticed a while back that my CPU fan was getting very loud anytime I played any games, so I took the fan and heat sink off and cleaned them. It had some grey gunk on the back which I suppose was a thermal pad. It was mostly in tact so I just put it all back together. Well, it still seemed to be kicking the fan into high gear a lot of the time. So I installed speedfan, and with no load it would read between 50c and 60c, then while playing flash video or anything else more intensive than typical web browsing, it would shoot up to around 70c and start to sound like it was going to take off again.

So I just went out and bought a tube of thermal grease (the white kind), wiped all the grey gunk off the cpu and heatsink, and applied some thermal paste. I think I applied a little too much, but to my surprise it's now idling at around 60c, and if I try to load any flash or anything it shoots up as high as 80c now.

So I guess my question is, could misapplying the thermal paste make it hotter than it was with the old pad or pre-applied paste or whatever was on there before?

I didn't use alcohol to clean the heatsink as I don't have any, but could that really make such a huge difference? Both surfaces were visibly spotless.