Internet Connection Sharing.
Here's the setup
2 Network Cards:
3Com Etherlink XL 10/100 PCI -> Cable Modem
Linksys LNE100TX(v5) 10/100 PCI -> LAN
for about 2 months it was happily doing NAT with no problems but all of sudden...
ICS went fubar, client computers (2 running win 98, 1 running 95) could not access the internet and the host system (mine) running windows 2000 developed an unusual problem on boot up.
On booting explorer (folders, browser, my network places, network properties) was unresponsive as was Opera (the browser) but other programs ran (albeit slowly) like Nero.
Upon checking the task manager I could that processes for the programs had started but no tasks. The CPU was at idle.
After about 15 minutes everything I was trying to open sprang to life but ICS still wasn't working. It's not handing out IPs (DHCP) or anything.
During all this my computer can still access the internet.
Now whever I enable/disable ICS in the network properties and hit 'OK' the dialog box freezes up. If I do a END PROGRAM and go back to it looks as if the option has been changed. When I disable everything works fine as far as booting up.