Hi Brandon, I think we figured figured out what happened on another forum. I think what happened is that I did have Cubase LE4.0 (or something like that), and it was at that time when I locked the tracks. But then, a day or so afterward, I installed an update to 4.13, which seems to have removed the lock/unlock option.... that's really the only thing I can think what happened.
And no, I didn't freeze/ unfreeze any midi tracks.... Haha, I'm still trying to figure out what freezing and unfreezing does.
One thing that someone suggested which seems to have worked, is to export the file out as a midi file, then reopen it. That seemed to of done the trick, it removed the locks from the tracks. Then I just saved the file over the old file.
I'm learning more by the day, but I'm still a newb for the most part.
Thanks for your help Brandon, I appreciate it.