There may have been a power surge when the battery was hooked up, or the dealer may have connected the battery backwards briefly. They probably didn’t, as you’d likely have many more problems than just the radio if they had. If resetting it again doesn’t work, you may be better off either seeing if you can find a similar radio from a salvage yard, or going with an aftermarket radio from Crutchfield.com or elsewhere. If you go with an aftermarket radio, you can get a better sounding radio with modern features like USB, mp3/wma, Bluetooth, and XM or HD radio, and iPod integration.
Good luck