Swiftech mcx-462 problem

[machu]

About a month ago I installed Swiftech on GA-7VTXE and 1600+. Yesterday I wanted to remove the fan that came with it and replace it with my new quiet Pabst. As I got to removing the old fan I noticed that all four screws that hold the heatsink to the motherboard got very lose. I tried to tighten them up but it is impossible because all standoffs (4 screws that you mount into motherboard holes) are turning with the screws. I'm pretty pissed about having to uninstall my motherboard again, but I'm even more pissed about the fact that $70 heatsink that was suppose to be perfect loses it's capabilities as the time goes by (by becoming lose). Am I missing something here??? I followed the mounting instructions to the letter! What are your experiences with this HS?