Geo's tip for breaking the slump...
This works for either sex (I've seen it) and while some what horrible and disrespectful both to the other person and yourself, it's worked for friends of mine.
What you need to do is go find the ugliest/nerdiest/least desirable member of the opposite sex (the bigger the dud the better) and hook up with them...go as far as you would normally go with someone you were really into OR until you lose all respect for yourself - whichever comes first. For the guys this means that you sleep with your slumpbuster...girls, I have no idea how far they'll go, but my friend went all the way.
Do this once (I can't stress this enough) and within two weekends you'll be out of your slump. Probably has something to do with lowering of standards, or confidence or something on why it works. Why it works for guys also plays of the fact that as soon as a guy has hooked up with someone he immediatly gets more attention from other girls. It's like he sends off signals that yes, some girl has approved him and he's safe for all of them...
Anyway try it...it couldn't hurt