Help! MP freeze after 20 sec in pictures, music or films (1 Viewer)

[ReadyOrNot]

TV-Server Version: 1.0
MediaPortal Version: 1.0
MediaPortal Skin: blue3
Windows Version: xp sp2
CPU Type: amd
HDD:
Memory:
Motherboard:
Video Card: ati x1200
Video Card Driver:
Sound Card:
Sound Card AC3:
Sound Card Driver:
1. TV Card:
1. TV Card Type:
1. TV Card Driver:
2. TV Card:
2. TV Card Type:
2. TV Card Driver:
3. TV Card:
3. TV Card Type:
3. TV Card Driver:
4. TV Card:
4. TV Card Type:
4. TV Card Driver:
MPEG2 Video Codec:
MPEG2 Audio Codec:
h.264 Video Codec:
Satelite/CableTV Provider:
HTPC Case:
Cooling:
Power Supply:
Remote:
TV:
TV - HTPC Connection:

HELP, new HTPC, fresh XP installed, after 20 sec when switching thru the pictures, music or film. MP Freezes
ALT+enter, unfreezes, but then after 20 sec, freeze again
The error log:
2009-01-06 23:25:51.562500 [ERROR][MPMain]: source :Microsoft.DirectX.Direct3D
2009-01-06 23:25:51.562500 [ERROR][MPMain]: stacktrace: at Microsoft.DirectX.Direct3D.Device.PresentInternal(tagRECT* sourceRectangle, tagRECT* destRectangle, IntPtr overrideWindow)
at Microsoft.DirectX.Direct3D.Device.PresentInternal(tagRECT* sourceRectangle, tagRECT* destRectangle, Control overrideWindow)
at Microsoft.DirectX.Direct3D.Device.Present()

Seems to be a problem with the directx, but what?