Vista and projector display issue

[silver]

Just had three projectors installed. Two are fine but one isn't. If you try and show both the laptop display and the whiteboard display, the image flashes.

We had this before on a dell 520 and it was resolved by reducing the resolution on the laptop. This hasn't worked in this case and the only other unusual thing is that this computer is Vista.

We have tried other XP machines on the system and all is fine.

Can anyone help - I have reduced the refresh rate as well but it didn't help!

[DevilsAdvocate]

Update display drivers?

[silver]

tried that - no go