I can't hold down a conversation in a civilized setting

For instance, I was introduced to a rather attractive bird who'd worked at the place before I arrived and all I could think was, "You're fit, so fit" and ended up blubbering something like, "So, you think Floyd Mayweather is pound for pound the best ever?" and she was like, "I don't really know who that is, sorry." And my boss just smiled and said, "Bret really likes his boxing. I bet he could tell you how many grams of fat are in that salmon appetizer too." I could have done, but refrained.

how about reading a daily newspaper? try and remember a few interesting stories each day and chat about them at parties/get-togethers.

it might also help if you refrained from anything sex-related, ex-related (nobody's interested, seriously), drink-related, anything to do with belief systems, sports, negative comments on other people's looks and politics.

a good idea is to ask (polite) questions about the person you're interacting with: where are you from, what/where did you study, what's your opinion on x, what are your hobbies and the classic is to let them tell you everything about their (adorable) children and look at the photos.

that might sound terribly boring, but it'll make you more likeable and that's all that really matters, isn't it?

it might also help if you got yourself interested in more "american" topics like baseball and stuff like that (for talking with men).

"So, you think Floyd Mayweather is pound for pound the best ever?"

I would say Sugar Ray Robinson or Henry Armstrong,myself.
You have my sympathies....

I usually get tired of the usual questions, especially during freshers' week etc - "What are you studying? Where are you staying?" etc. I like questions like "raspberry jam or marmelade" to start conversations with strangers. Then I talk incessantly about music.

A good one is "How much does a polar bear weigh?"
"I don't know, but enough to break the ice"

I've never been much good at conversing, especially with girls, which is why I joined a drinking society at university, so I could get drunk myself, talk to drunk girls and get laid. While taking the romance out of things, it didn't require thinking up witty one-liners, being charming and generally coming off as a well-rounded man. Now I've left that scene, I just can't seem to talk to girls and the high ranking people I'm supposed to engage with professionally.

Sure, when I'm back home in the UK I can go down the pub and joke around with the simple minded pub men and play tennis or go on runs with my university/ school friends and I do fine. But without being plastered and "bantering" girls, of who in the past 90% would walk away while the other 10% would end up pulling me, I can't seem to get anywhere. That's because in California everyone has to drive everywhere, so getting drunk on a night out at a bar isn't really an option, and if you do get drunk (carpooling of course), the blonde beach babes sipping on their mojitos will look at you like an idiot--not even the English accent can get you out of that one. In the end I just falter, there are awkward silences, and I'm closed out. I look like a socially awkward geek.

The reason for this, I believe, is my highly restricted range of conversational topics. I realized just today that I have five topics of conversation 1) Boxing. 2) What a slag my ex girlfriend is. 3) English, French, Spanish and Argentine Football 4) Diet, nutrition and working out. 5) Late 20th century US political and cultural history.

This limited range is causing trouble in my work life as well. Today I was at a cocktail party, which I knew was likely to be boring, but turned out to be mind numbingly so. But I was expected to be there and to at least make small talk. Everyone else seemed so adept at this, seamlessly moving from group to group, mingling with people they hadn't spoken to before. But with me there were awkward silences and I just couldn't fill them. I got more and more agitated, worrying that they would think me boring, socially awkward, or intense. So I did my best but came off a complete knob. For instance, I was introduced to a rather attractive bird who'd worked at the place before I arrived and all I could think was, "You're fit, so fit" and ended up blubbering something like, "So, you think Floyd Mayweather is pound for pound the best ever?" and she was like, "I don't really know who that is, sorry." And my boss just smiled and said, "Bret really likes his boxing. I bet he could tell you how many grams of fat are in that salmon appetizer too." I could have done, but refrained.

Basically, girls don't want to know about any of the above topics (I lost a girl I was seeing because I kept mentioning my ex's sexual past) and neither do my colleagues (unless they, too, are historians and we're at a conference). I need to know how to move beyond them in a social setting while remaining sober and polite. Do you think I have OCD or something which keeps me from thinking about other things, and has anyone else had similar problems with social interaction and awkwardness which threaten not only relationships and potential relationships, but career prospects?

Your career requires attending history conferences and working the room at cocktail parties? Are you CEO of a textbook publishing company or something?