WMI and ICS
I am having EXACTLY the same problem as downunderground.
Everything was apparently working fine and I was sharing the internet over the host (Win XP) to a client (Win 98SE) with no problems.
Then mysteriously internet connection sharing stopped working. Sharing files, etc over the network still worked fine. When I tried running the network setup wizard to re-establish ICS, it said there was an error meaning the wizard could not be completed.
Checking properties for the LAN and for the internet connection, like downunderground I noticed too that under the Advanced tab it said that it can't display information as Windows management information may be corrupted. It suggests using system restore to restore to an earlier point. I too tried this, only to find that whatever point I pick, when Windows restarts it informs me that the restore failed due to an improper shutdown! (which must be a problem in itself... I can't understand what is improper about the way my computer shuts down!!!)
Anyway, I ran the system file checker ('sfc'), as suggested, but while it ran OK it didn't help. The network setup wizard still won't complete, and the connections properties won't display information in the Advanced Tab relating to ICS.
Does anyone have any suggestions short of reinstalling Windows XP? I have been using Windows XP for a few months but these seemingly inexplicable problems are irritating and almost make me want to go back to Win 98 SE!!!