XP Pro Sp3 does not sleep

Hello

I have custom build PC which I am running XP Pro SP3

Since I upgraded to Frodo I can not make it sleep (suspend ) with my MCE when XBMC running.

Here are 3 different scenarios

I could make my PC sleep when XBMC is NOT running
I could make my PC sleep when XBMC is running via its shutdown menu ( with Suspend selection )
I could not make my PC fully sleep when XBMC is running via my MCE switch of button. What happens is Video Card is stopping the signal so display gone black but PC is still running but can not access it so you need to reset. My PC is connected to my Philiphs LCD TV via HDMI and my Video Card is RADEON HD 5450

How can I troubleshoot this problem ? It is so annoying.

Thanks