This is a common issue with nV and Apple monitors too.
All cards can be forced to support resolutions outside of their 'norm', just not outside of their maxes (usually related to a refresh rate/colour depth). But it also depends on the spanning modes you have a choice of like nV's usual 3200x1024 and 3200x1200.
You often need another program to get them to match specific resolutions like <A HREF="http://entechtaiwan.net/util/ps.shtm" target="_new">PowerStrip</A> or see if nV's quick way works for ya'.
<A HREF="http://www.nvidia.com/object/custom_resolutions.html" target="_new">http://www.nvidia.com/object/custom_resolutions.html</A>
From what I've read though there's a dual monitor bug with this, and nV drivers do not support this out of the box (like they won't support Apple Cinema monitors as such).
There's also a reg hack that I got from TweakXP to force 1400x1152 for my editing rig (<font color=red>Use at your own risk</font color=red>, VERY RISKY and LAST RESORT if you're not familiar with editing the register, don't bother with this!);
<A HREF="http://www.tweakxp.com/tweak823.aspx" target="_new">http://www.tweakxp.com/tweak823.aspx</A>
- You need a licence to buy a gun, but they'll sell anyone a stamp <i>(or internet account)</i> ! - <A HREF="http://www.redgreen.com/" target="_new"><font color=green>RED </font color=green> <font color=red> GREEN</font color=red></A> GA to SK