Sounds like you might be using the Enter key on the number pad, which is a column break (and if you only have one column per page or frame it moves on to then next one).
If you aren't using the number pad, chances are you're on a windows laptop and have a bios that maps the two enter keys together, and the behavior will change depending on the state of the numlock key. If that's the case, let us know and we can tell you how to make custom keyboard shorcuts to work around the problem.
Peter, thank you so much! Your diagnosis was right on. I was using the ENTER key on the numeric pad, and by default this Windows XP laptop boots up with the numlock key turned ON. Using the proper ENTER key corrected the problem right away.
Thanks again. I had uninstalled and re-installed twice with no success!!