flex4, flash player 10.1 in debugger hangs up the movie

My flash swf generated in Flex4 has a strange behaviour:

When it is runs in the Flash Player Debugger, it hangs the flash player : Flash player is then taking 25% of CPU and I have to CTRL ACT SUP kill it.

When it runs in the Flash Player, it works normally.

This only happens with 1 of my devlopment which is a kind of MIDI player in Flash (all otehr flex devlopments work fine in Debugger and in Normal player.

I put it in the http//www.proxymis.com/test.swf so开发者_StackOverflow you can test it in debuuger player and normal player

Any idea why this happens and how to solve that ?