Issue with dual screen mirroring

[itorra]

On rig 10.6.4 (w/ last snow graphic update), p45-ds3l, 8500gt

 

nVidia GeForce 8500 GT:

 Chipset Model:	nVidia GeForce 8500 GT
 Type:	GPU
 Bus:	PCIe
 Slot:	PCI
 PCIe Lane Width:	x16
 VRAM (Total):	512 MB
 Vendor:	NVIDIA (0x10de)
 Device ID:	0x0421
 Revision ID:	0x00a1
 ROM Revision:	nVidia GeForce 8500 GT OpenGL Engine
 Displays:
SyncMaster:
 Resolution:	1680 x 1050 @ 60 Hz
 Pixel Depth:	32-Bit Color (ARGB8888)
 Main Display:	Yes
 Mirror:	Off
 Online:	Yes
 Rotation:	Supported
SAMSUNG:
 Resolution:	1680 x 1050 @ 60 Hz
 Pixel Depth:	32-Bit Color (ARGB8888)
 Mirror:	Off
 Online:	Yes
 Rotation:	Supported

 

As you can see my main work screen (SyncMaster - which is 22" 226bw) is connected in DVI and my 37" wide-screen TV is connected through VGA cable.

When I put V in Mirror Display the content is shown only on the TV and on SyncMaster all I see is just a blue screen and the pointer that behaves exactly like on TV display.