it could be connecting to bad peers try clicking view/show/hide put a check next to connections then you can remove then also do you have peerguardian or peerblock if not you should get either one it blocks bad peers. i have been using peerblock sense i have vista peerguardian doesn't work very well with it get pg2 here
Phoenix Labs PeerGuardian 2 or peerblock here
PeerBlock ? Peerblock Site if you have vista and want peerguardian get the one for vista but its new and has problems.