does gpu-z see the card?? have you check that the card fan is moving?? if it dust bound or failed the gpu could have over heated. if gpu-z cant read the card right then the card may have died.
smorizio, correct me if I am wrong here, but, if the card died would it display anything at all?
He is still getting 16 bit color and a low resolution.
To me that sounds more like settings/driver issues.