Unwanted drop down menus

I have 12 forms in a folder, I've created fill in fields on each for in Acrobat 8.0 Pro. These forms have no link between any of them, yet when I double click on some fields (not all fields) a menu appears with various choices sometime not even matching the format for that field. In some cases when I change the name the drop down goes away, other fields it doesn't seem to matter what I do. I've gone so far as to recreate the field, give it a new name and I still get a drop down.

Any ideas as to how and why this happens? Any suggestions as to how to stop it from happening?

Bob Ht