One thing i have noticed in my time making flash, is its not good to mix timers and enter frame effects. (this is just my opinion)
I would either recommend using timers for EVERYTHING or enterframe events for EVERYTHING. When you use only one, everything is linked together, so computer speed doesn't effect ability to preform a task.
If you want my personal opinion, i like making games with enterframe events for everything, because if you computer lags it does not hinder your ability to play the game (as much as if you do it the other way).