I hate socializing in a group. I'm OK (not great, but OK) one-on-one because I know who I'm talking to, whereas in a group, I'm unsure to whom i should direct my comments. Although I have a hard time relating to people in general, I do try to connect with the person to whom I am speaking; however with more than one person, it seems almost impossible to do so. Also, being rather shy and self-conscious, the more people there are, the less likely I am to speak up.
Also, I absolutely refuse to do any sort of public speaking. My sister got married a few years ago and as the matron of honor, I was approached by the wedding director to give a toast. I refused, which apparently annoyed the best man. He told me that it's one of those thing nobody likes to do, but you do it anyway. I'm sorry, but no. My sister understood and was completely ok with it. Besides, I can guarantee that if I were to stand up there and try to give a toast in front of all those people, I'd embarrass myself and make everyone else very uncomfortable. So I didn't do it. It's not something I need to get used to, get over, or anything else. It's just something I don't do. And surprisingly enough, the reception went on, people danced and had a good time, and my sister's marriage is still valid.