I doubt it is the card - outputting 1080p shouldn't be a challenge for old cards let alone current ones. It may be that your monitors native resolution isn't being detected.
I would suggest the first thing is head over to the Viewsonic product page
and get the correct driver.Windows 7 32bitWindows 7 64bit
Next thing I'd do is get the latest drivers for your video card, and then uninstall the current software/drivers, reboot and then install the new drivers.