Social Problems! Help?

I feel like there are certain people at work who either do not like me very much or are just very cold and snobby towards me. I can't really figure out what, if anything, I ever did to bother these people. Some of them just act like if you're not in their little clique, you might as well be invisible. If I try to be light-hearted and joke with them, nobody laughs, but every time they have a joke between each other, they laugh hysterically. I've tried to figure out what it is about me that's bothering them so I can stop it, and I have no answers. Outside work, I don't seem to get this reaction from many people. Does this happen to anyone else out there? Is there something wrong that I can fix? Help!