Why can't I import Individual Prefixes into the database?
Why?, well I have no idea (sorry to dissapoint!)

How to get around - well, it would appear that civi requires the numeric Value (1,2,3), rather than the label (Mr, Mrs etc) for the option. To find the values for substitution one can go to:


  administer > System Settings > Option Groups 


and hit the "options" link to the right of "Individual Contact Prefixes". The prefixes in your csv will need to be substituted with these values.

Hope that helps...