error message running et on high end lcd monitor/tv

I am running ET on the Sony Laptop VGN-FZ11S (runs acceptable under different resolutions from 800 x 600 to 1280 x800)

Now I tried to plug in the monitor/tv Sony KDL-52X2000 for watching ettv matches but I cant get ET to work via that monitor.

Watching movies or surfing the web via HDMI cable set up as second monitor is not a problem with that Sony monitor/tv - works perfectly under all set resolutions from 800 x 600 to 1920 x 1080 pixels and 32 bits color depths.

When i change via vista display settings to the extern monitor as primary and shut down the laptop display and try ET to start with the resolution of 856x480 pixels (widescreen) and color depth of 16 bits i get the following error message in the open GL box.

___________________________________________________________

C:\GAMES\WOLFEN~1/etmain

----------------------
3763 files in pk3 files
execing default.cfg
couldn't exec language.cfg
execing profiles/hal/etconfig.cfg
couldn't exec autoexec.cfg
Hunk_Clear: reset the hunk ok
...detecting CPU, found Intel Pentium III
Bypassing CD checks
----- Client Initialization -----
----- Initializing Renderer ----
-------------------------------
----- Client Initialization Complete -----
----- R_Init -----
Initializing OpenGL subsystem
...initializing QGL
...calling LoadLibrary( 'C:\Windows\system32\opengl32.dll' ): succeeded
...setting mode 11: 856 480 FS
...using desktop display depth of 16
...calling CDS: failed, bad mode
...trying next higher resolution: ok
...registered window class
...created window@0,0 (856x480)
Initializing OpenGL driver
...getting DC: succeeded
...GLW_ChoosePFD( 16, 16, 0 )
...113 PFDs found
...hardware acceleration found
...PIXELFORMAT 7 selected
...creating GL context: failed
...failed hard
...restoring display settings
...WARNING: could not set the given mode (11)
...setting mode 11: 856 480 FS
...using colorsbits of 16
...calling CDS: failed, bad mode
...trying next higher resolution: ok
...created window@0,0 (856x480)
Initializing OpenGL driver
----- CL_Shutdown -----
RE_Shutdown( 1 )
Shutting down OpenGL subsystem
...wglMakeCurrent( NULL, NULL ): failed
...releasing DC: failed
...destroying window
...resetting display
...shutting down QGL
...unloading OpenGL DLL
-----------------------
Q_strncpyz: NULL src

---------------------- end of message -------------------------------------

any solutions ? - for any help my eternal gratitude will be ensured

cheers hal