I use Ares, but I suppose this applies to any one of those programs. What is going on when the status of the file you are trying to transfer is "connecting?" Right now my program is showing that it has found a bunch of users for said file, but it's been "connecting" for quite a while now. Would restarting Ares help?
Edit: I just answered my own question by restarting it, and it does help. But still, what's going on when it's connecting for like a ridiculous amount of time to no avail?