Operating system, please....
You say "return" which implies Mac, but that may not be, and it further implies the key on the alphabetic keyboard, but it sounds like you are hitting the Enter key on the numberpad, and that, by default, is the shorcut for column break and will produce precisely the behavior you see. The only thing odd about your description is that it works OK the socond time, but I'm guessing you're switching to the key on the alpha pad when you do this (perhaps unconsciously).
Im working from a PC, Windows 7.
Ive always called it the return key regardless of Mac or PC, and the one on the numeric pad the Enter button as labeled. But I know what your saying in terms of the 2 buttons having different fuctions. I know they have different fuctions so I would not imagine I do that, but as you say perhaps unconsciously I have been. I will keep an eye on that over the next few days.
Thanks for your response
Oh Im a dumb ***!
I had moved my mouse and keyboard arrangement. My mouse sits right by the Enter key now and I was hitting that without thinking as the Return key.
Cant believe I had not noticed my self doing that.
OK, that's a new one.
But you probably don't want to be pressing the enter key on the numpad, either.