Timer and MMControl

I have a CD Player and a visualization running at the same time. The problem is that the CD Player goes off the MMControl and the visualization goes off of a timer. When the timer is going, the MMControl does not accept any commands from the user. I can't control it at all. When I take out the timer, it works again. Why is this, and what can I do to stop it or get around it?

thanks in advance,

bob