I had a problem where IIS process w3wp.exe where going through the roof. It consumed 100% of CPU and all the RAM that was available. After a IISRESET it when`t down again. This happened a couple of times a day.
First I though that this was because some modifications to the web.config file that I did. But recovering the original files didn`t help.
After A LOT of hair pulling I found this KB. And it worked! Now the server is running like a kitten 🙂