Hmmm...from the "Doc education side of things", I can totally relate to what you mean. Some people you really do just "click" with. It's like a magnetic attraction, and Docs & "Scientific researchers" have all their hypotheses about why and how...but I don't think anyone can really fully explain it. It's one of those things that "just is".
To be honest, as a fairly outgoing & charming individual in the office and real life in general, I have to be somewhat careful about that myself. Don't get me wrong at all - happily married with a soon to be 8 year old daughter (Kat turns 8 tomorrow! ), and everyone knows that, including the Mrs. DrPop; but there are those moments where you just groove with someone of the opposite sex without the rational part of your mind necessarily realizing what's going on . . .