Ok, here's the deal. Forgive me for the background but it is necessary. A while back some of you might remember that when I got my 2500+ M I bought some AS Ceramique and a cheap Zalman copper flower HS with a 90mm fan that mounts with a bracket on the PCI slots. I think it was the CNPS3100+. It served me reasonably well - I hit 2.5GHz quite easily at 1.7v with temps floating around 45-46 idle and 53-54 during Prime95. That seemed too high, so I got the Thermalright SLK-900. I was expecting at least 3-4 degrees difference, because, afterall, the thing is highly reputed here and practically everywhere. The first time I installed it (w/ AS Ceramique), the temperatures were higher. Now let me tell you that I kept the same 90mm fan the Zalman used, which is actually quite silent and runs at 2600RPMS. My logic was this - since the CNPS3100+ worked fine with the Zalman fan, so would the SLK-900, and I could witness a difference strictly in the heat dissipating properties of the HS alone. For a comparison:

CNPS3100+ w/ Zalman 90mm fan = 45* idle, 54* load (rounding up)
SLK-900a w/ Zalman 90mm fan = 48* idle, 57 * load

This pissed me off. So, I reseated the HS. No difference. I reseated it once more, being soooo careful with my AS Ceramique as to get it perfectly distributed on the core. Put the SLK-900 on, and finally temps were about the same as with the CNPS3100+. However, this made me even more mad! After spending 30 mins putting some stupid thermal compound on correctly, I couldn't get the highly reputed $40 heatsink to perform as well as a $15 bargain heatsink. I've lived with this to this day, running the machine at 2.2GHz 1.575v nearly the whole time to make things a little bit cooler.

Yesterday I was cleaning my room and decided to try refitting the heatsink and going for a high overclock which I could subconsciously permit and sustain. I got the stuff on there perfectly, being sure to clean off the gunk from the last application thoroughly. I put it on, took it upstairs and flipped the switch. Got into the bios, set it for 200x12.5 1.7v for 2.5GHz. Loaded windows, and checked my hardware monitoring program that came with my NF7-S, along with nVidia's nForce2 System Utility. Both showed temperatures in the mid 50s at IDLE. To make matters worse, while I was programs such as Photoshop, the machine shut off and the warning beep emitted from the Mobo. The CPU had hit 60*, and even though the NF7-S' warning temperature is set to 90*, it shut down anyway. What could be causing this problem?

Anyways people, are there any suggestions out there as to what in the world could be going on? Yes, I dusted the heatsink with compressed air along with the fan before putting them back on, and I was practically sure that I had put the Ceramique on perfectly. I don't know what to do, and am considering putting my CNPS3100+ back on to see if anything improves.