For *any* profile field you create or for a particular one? Can we see an image or what you are talking about? Have you checked to see if this is true on a totally default style also?
Create a new style with no parent:
- Styles & Templates > Style Manager > Add New Style
- Parent Style: No Parent Style
- Title: Default vBulletin
- Allow User Selection: Yes
- Save
Then browse the site using that totally default vbulletin style - do you still have the same problem?