I had this same thing happen to me with the country field.

Originally, I deleted all of the countries except Canada and USA.  I had a third option, "Country not listed ...".  Then I offered a "Country not listed:" field where members could enter their country if it wasn't listed in the drop down.

My plan was to only add countries to the Country drop down as new members needed to have their country listed.  That way, I wouldn't have an unnecessarily huge list of countries.  i.e.  I don't think I will get a lot of signups from China or India.

In any event, I found when I went to add a new country and reorder the list (to keep Canada and USA and "Country not listed ..." at the top and the rest of the countries in alpha order, all of my existing members' country selections would disappear from the system.  When I visited their profile, they all said my default "Not yet disclosed." (or "I'll tell you later.")  I had to go into each member and manually reselect their country.

Is this normal behaviour?  I would think I should be able to add countries or reorder them, with it effecting my members' data.  Of course, if I were to rename an existing country, that would effect a member's data (i.e.  If I renamed "USA" to some other country name, then that would effect those who have chosen USA.

But should added and reordering a field's items cause the system to clear out all of the members' data for that field?

Thanks,
Glen