Aspergers is one prime example, people with this disorder tend to have higher IQ's according to recent research but have inefficient social skills
Maybe it's just the hypochondriac in me but I've often thought that I have a mild case of it. Actually, when I probe deeper into myself (ooh, that sounds...kinky) and really psycho-analyze my behavior it's pretty clear to me why my one on one social skills tend to lack with all but the closest of friends (and my g/f).