This is an oldie, but goodie... It seems to be connected to page file usage (virtual memory) in Windows. Try defragmenting your disk first of all. Also try defragmenting your page file with PageDefrag from Sysinternals (free utility download). There's also some advice at Curious Labs. However the problem will probably come back to bite you later - it did me. I finally fixed it for good by creating a new partition on my HD, and putting Windows' swap file on there by itself. That's a bit extreme, however, and you probably won't want to do that in the middle of a project. The first two options should "unstick" you for now.