Autofill
Hey Siron,
Not sure if you have resolved the problem, had the same problem myself so that is how I stumbled upon your post.
Not sure if this helps or not but if you go to safari -> preferences -> autofill tab, there are three autofill options to choose from.
Like wrldwzrd89 said, make sure your information is correct in your address book and then edit "other form" and just delete everything and start all over.
Like I said, not sure if this will help but the only way I could fix it was just delete all previous autofill entries and start all over.
Hope this helps.