Frustration / simple question

I am really frustrated with this, but I think it would be a simple question to answer to someone that knows Actionscript.

Here is the question (which has caused be hours of agravation!):

If I have simple actions on the first frame (Ex. trace("this is first frame");) Everything works great when I test the movie (I get my trace line).

BUT....if I step forward to the next frame and then go back to this same frame, the frame action is never executed (I never get a trace line) again. WHY ?????

This is confusing! Shouldn't the action for the frame execute whenever the frame is stepped into?

Please help...and thanks in advance for your time.

Thanks,

Oleg