You need to go to your account page on Slush and add a worker. Then use THAT login/pw to get it going.
ps -- sorry about the NVidia card
this doesn't really help me at all.. and what about using NVidia card..?
ATI Cards are around 3-4 times faster than NVidia cards at the moment... I have dual GTX260s at the mo and they get 50MHash/s each, whereas a sinlge 5850 can get 300MHash/s or so! I am going to be upgrading to a triple 5850 system soon.