I had a similar problem during this weekend's contest: I'd enter a state
(say CO) and N1MM would say its not a valid state. I'd type CO over and
it would be accepted.
I think what might be happening had to do with the check partial
capability with N1MM. Here's what I think happened. And it happened
rarely. I'd type in a call for the station calling me and if they were
in the check log N1MM loaded their state/ section. However, if I typed
the call in wrong I'd fix it in the call entry window and then try to
log the contact. This is when the " not correct section" or whatever
the error message was would come up. At least this is my guess on what
happened. I didn't take notes during the contest as it happened so rarely.