I mourned the social situation at school for a solid month at the beginning of last (1st year) semester. I've been out of college for awhile, so the cliquishness caught me very off-guard. Then, the beautiful, dazzling epiphany - the friends I made before I entered med school did not vanish from the face of the earth the day I first gazed upon my rotting cadaver. So, my social life (ok, ok, what social life I have... ;-) remains elsewhere, and it works out really well that way for me. Harder when you've just moved to a new area, but you can surely make it work, meeting people through your dance class/rugby team/church/local neighborhood bar/whatever.
And as far as med school classmates (and generally in life with regard to people's interpersonal behavior), here's my advice - maintain low expectations, and you'll be pleasantly surprised! (Although I really have to admit, there are some mindbogglingly nasty & obnoxious people out there - I try to remind myself that there's surely some reason they have become this way, and perhaps I'd be the same way if I were in their shoes. Doesn't help all that much, though.)
Also, as others have said, you probably don't know ALL that many of your classmates, unless you're at a quite small school - and I often think some of the most interesting people are hidden in the "low-profile" crowd.
Finally, I can't help but think that all this social angst is rather brief and artificial. I was out "in the workforce" for 7 years, and fer cryin' out loud, despite the fact that you were stuck in the office, lab, or on the road with people maybe 50, 60 hours a week, no one took work social stuff all that seriously. At the end of the day, everybody went home to their girlfriend/boyfriend/husband/wife/kids/TiVo, enjoyed their hobbies, and maybe went to happy hour or a club with some like-minded colleagues if they felt like it. Big whoop. While at work, you enjoyed working with/hanging out with the fun people, and rolled your eyes at the irritating ones. Maybe talked a little trash about their crappy Java programming abilities if you were feeling really savage. Going from a youngish engineering/research work environment to 1st year med school, the environmental social angst quotient has skyrocketed. I've been a little flabbergasted by it, but I'm thinking it's age-appropriate and normal for a school environment. It won't last that long.
Alright, enough procrastinating. 2 weeks worth of accumulated laundry await. So cathartic...