Considering you're using twitter talk in an area that doesn't need it, and the fact that you're making accusations without actual proof, I'd say you ARE careless. I'm not assuming it, you're just proving it to me.
That's not a memory leak. That's windows' disk cache being stupid. A memory leak would be visible in task manager under the process that is leaking. In the case of uTorrent, the INSTANT the process exceeded 2GB of ram, it would crash.
Considering you do have zonealarm and the original poster doesn't, you have thread hijacked. And if you search on these forums, you'll find that zonealarm is more trouble than it's worth.