I’ve downloaded your fla and have some comments:

First your script is unorganized. For example: You have script for the mountains on lines 5, 6 and 8, then again on line 20 and 21, and again on line 46. I like to keep my script ‘tidy’, so that if I have a problem with the mountains, I don’t have to scroll through lines of unrelated script to find the one or two lines I’m looking for. If you spend a few minutes rearranging the script, you might be able to see what problems you have.

You have the balloon mcs as animated movie clips. I would have the balloons rise using action script.

There is a missing bracket or parentheses somewhere (or maybe reversed). I was only able to glance through quickly but something just doesn’t look/work right. I'm getting output errors.