well, that was a fluff.
i was trying to set up a span desktop on a nvidia geforce 5200 fx
two identical viewsonic va2226w lcd panels (not my kit, unfortunately).
we wanted to run at native resolution (1680×1050) on each.

man, nowt but touble., updatred the drivers, tried the omegas (they crashed the system) but no luck. 1680×1050 and 1600×1200 was all i could get (ie one of them out)

then i had a moment of inspiration. yep. one was on analogue, the other on digital (d-sub vs dvi)

and it was the dvi that couldn’t cope.

changing them both to analogue using a dvi to dsub converter solved the problem, now they are both running at native.

i’ve blogged this so some other poor person desperately trying to fix thier similarily failing dual headed 1680×1050 / 3360×1050 lcd geforce nightmare gets saved a few hours.