It might be a graphical issue, i had a similar problem when i had just installed. what size screen are you using? the defaults set the refresh rate too high for a 15" screen, try pluging in a bigger screen(if you've got one?!) and you might see something. then it's just a case of downloading the nvdia restricted drivers through the synapse manager..
EDIT: NB. instead of a bigger screen anything with a greater range of allowable refresh rates will work e.g. maybe an old CRT you have somewhere?