Hi James, and thanks for the reply.
The PC has always been in Aero. Ever since installing the OS about six months ago. The theme is the basic "Harmony" one.
For the meantime (this is my Work-Computer), I've added the ATI card as a secondary video card and am using that to run the extra monitor. It's not ideal as the reason I wanted to use the DL adapter is that this monitor, while being DVI-D, does not appreciate DVI cables longer than a metre - it loses sync. A lot.
I've tried several different cables of varying quality, and the result is always the same: occasional drop-outs.
With the DL adapter in place, the display is reliable, as long as -
I don't start up or shut down my workstation, or blank the screens to save electricity...
Like I said, this is my work computer, and as such I have to use it all-day, pretty much every day.
If you can think of anything not too disruptive to try (during the week), I'm very happy to give it a shot, but it might not be until the weekend before I can do more drastic testing - If I trash my PC during the week, I'm in BIG trouble.
Regards, and thanks again,
Susi xx