Word(s) fail(s) me

I just attempted to type a sentence about Nino Burjanadze, calling her "Mrs. Burjanadze", and had this bizarre experience:

First, Word's spell checker rejected "Mrs." No, it's not British; it suggested "Mrs." as a replacement. Though if I accepted that suggestion, it kept on rejecting it. I had to go in, erase the period, and let Word correct "Mrs" to "Mrs." before it would accept it.

But then Word informed me cheerfully that "Mrs." was a sentence fragment that I should consider revising.

Bill? This is why people hate your products.

(yes, I usually have this "tool" turned off; the paper I got for correcting had it turned on...)