pc upgraded resolution problem with 5770 graphics

[Targ]

im using DVI, via a DVI > vga adapter,

Your not actually using the digtial interface your using the Analog part of DVI which was included for compatabilty with VGA.

I know that a 5770 will produce 1920x1080 if you use a digital interface.

I am currently using a single 5870 to drive 3 - 24 inch displays each at 1920X1080

Seriously, try a DVI or HDMI cable and I think your problem will go away.
And you will get a better picture as well

There is the other possiblity that the monitor is not capable of 1920X1080 and the old video card was driving it at it maximum resolution of 1600X1200 even though you set it to 1920X1080.

-- edit if you open the Catalyst control Center and select "Display option" on the Graphics pull down tab it will show you the video adapter and in brackets the model number of the display that is connected to it, if the monitor supports that function.
then you would know for sure what resolutions it supports.