One or two things you might consder rechecking

1. did you key the camera to specific frame in the time slider?
2. try re-creating a new camera, does same thing happen to all the cameras?
and
3. hopefully there isn't a sticky that's turned for that camera, which i don't know (havent' checked) if there's one or not for cameras.

pretty much all that i can think of as of now ^^