I had the same problem initially,
You need to add a custom resolution in the nvidia control panel as per this post:
http://www.widescreengamingforum.com/node/9741
If the resolution already exists as a custom res, delete it first other wise it will not work.
Once you have this custom res, test and apply it.
You must also be using the PowerDesk-SE (GXM) beta version. i think the bersion number is 2.4.x.x.
Dont be alarmed if the 5040x1050 res is the Powerdesk does not work, as mine dont either.
Hope this helps
ok so now im getting close....
I have found out what i was doing wrong to get it to not display the OSD out of range.
I wasnt selecting the CVT Reduced Blank first. now i do see a picture when i go to custom resolutions... but
I enter all the details in and do test, it then says it will now set the custom display mode and revert back if I do not confirm within 15 secs.
once i select ok i am told custom mode test failed and it reverts back.
How do i save this custom mode?
im almost there