fsx crash at tod after descent clearence

I have a problem,I start my IFR flight and everything goes well until TOD.As soon as I get the descent clearence from the fsx atc I:

• cannot click left or right anymore
• hear a sound when I press a key ("windowsXP Ding.wav")
• can still use my yoke and rudder pedals

The problem is that I can not control my descent because the AT is on and is still set for cruise.I can get the autopilot off by pressing " Z " but I cannot aknowledge atc anymore or use my FMC, AP, AT etc.When this occurs, I press " Escape", then the Window does appear normaly but also here I can't click anything.I usually use ALT+TAB to swith to my desktop and then use taskmanager to quit fsx, since that's the only way.Is anyone familiar with this problem or does anyone know how to solve it?My computer specs are:

• CPU: Intel e8500 @3.16
• Mem: 4GB ddr2-800
• Grphx: nVidia gt9600
• Motherboard: Asus p5n-d
• HD: 7200rpm 500gb
• power supply: 850w
• OS: Windows XP proffesional SP3 32bit

All my drivers are up to dateFurther used:

• Saitek Proflight Yoke
• Saitek Proflight Rudderpedals

I use FSX SP2 with the following addons:

• FSacars
• FSUIPC
• UTX europe
• REX 2.0
• GEX europe
• MYtraffic X 5.2
• ariane 737-800 X2 advanced
• level-d 767
• Pmdg md11, 747 and j41
• carenado piper saratoga
• captain sim 757

Thanks in advance!Kind regards,dva270