Windows 7: nVIDIA GeForce 9500 GS and HP w2338h

I've been using Windows 7 RC (64bit) since it was released.

My monitor was displaying the full screen resolution of 1920 x 1080 and it was beautiful! Suddenly, yesterday, on boot-up, the screen resolution has "mutated," and I can't figure out how to get it back. The image is still crystal clear with full 32-bit color, but it no longer fills the entire screen.

Both the HP m9500y PC and HP w2338h 23" monitor, are capable of 1920 x 1080 resolution. Until yesterday, the entire screen of the monitor displayed a beautiful image to the edges of the screen. Now, however, the image leaves a one-inch black bar on the right. It's as though Windows 7 forgot how to "scale" the image to fill the entire screen. Also, round objects, such as desktop gadgets, are slightly elongated vertically where before they were perfectly round.

My connection is and has always been through the analog VGA port.

I use a KVM switch to switch between several PCs, two of which run XP SP3. Those PCs correctly scale the image to fit the entire monitor screen at a variety of resolutions, but the new Windows 7 PC seems to have "lost its mind."

Are there any tweaks I should be aware of? Has Microsoft released an automatic update that changed the interaction between the display hardware and software components?