Vista - Creating an Ad-Hoc Network? [REPOST]

I know this has been asked before, but I can't find a solution. I want to
set up an ad-hoc wireless network on my online PC so I can share its wired
Internet connection.

The set up proceeds for a while, then I get an error message "Windows could
not set up <name of network>". I've tried different security details, I get
the same message.

Note that I am trying to set up the network on the "first" PC, I have not
got to the point where I try to connect to it with a second PC.

--
Nigel M

If my question is about apples, please don't suggest bananas