SWF becomes slow in longer run

We have a software wich uses flash for UI, we show videos images and lot of action script code running behind the scene.
I am facing a serious problem in longer runs of the application.
If I keep my application open/running for long time, something like more than two hrs or so, application becomes slow, videos doesn’t play properly and even application responce time gets high.

First I thought it might be because of some memory leak, but it’s not.
If I start video (HD quality flv file 30-40MB file size) and leave the app as it is for more than 2 hrs or so, video becomes sluggish, memory usage is around 400 MB and my machine is not the cause as it’s a prety much new machine.

Please help me, I need to find some solution for this.