i had that happen recently, except i didn't remember any of the movie at all..though it seemed a part did remember watching it as the memories of the scenes were kind of there. it was very strange. it was a children's movie. i was completely confused. and the last time i watched it, one of the little's (or maybe more than one) was watching it too.

it wasn't the 'usual' knowing i watched a movie and not remembering as i will be able to know that i watched it and remember something about it better but just don't remember due to boredom or just tuning out for whatever reason.