Well, everything setup wise on the 6800 should be the same. Not sure what it takes to connect vista to an ad-hoc network. Fortunately, I'm still running XP on my PCs. Waiting for Service Pack 18 to release for Vista before I switch.
Might try running through those instructions again from scratch and see what happens. Oddly enough, sometimes repetition gets things to work on subsequent tries. Who knows why...