Lightroom :: Unwanted Duplication Of Picture Titles?

I had a batch of 42 photos and laboriously entered titles for each one. At about the 40th, I discovered the program had copied into all the picture titles the most recent title entered. So it had overwritten my work. I started over and entered titles again. This was not a synch action on my part and there were no efforts to have a repetitious action that might apply to the pictures included in my collection.
 
I will understand this is probably some kind of "feature" but if so where do I turn it off? This is Lightroom 4 and involves both raw and jpg files.