When I first started my last job, I kept calling my workmate Raewyn by the wrong name. Every time I called her Jan though, she eventually would respond - without correcting me. It must have been weeks before I realised, and only after I heard someone else call her by the correct name.
Today I did a similar thing, except in a way it was much worse. Worse, because the person I was offending was an external person, someone from whom I was requesting free booklets and stuff. Worse also because we were corresponding by email, and her name was clearly laid out under each reply. It was really embarrassing.
I think I'll blame the old pregnancy hormones. I didn't think to do it at the time, when I wrote my apology to her - but then that opens up the where-do-I-draw-the-line-with-broadcasting-my-pregnancy can of worms, anyway.