Can't connect to Windows 7 "hostednetwork"
Well, after tearing my hair out and feeling my hair became lighter, I gave up. But then, the wifi of the laptop became even flakier: It can no longer connect to the Office WiFi.

So, I did some drastic measures:


Uninstall all ThinkPad utilities that manage the wifi
Uninstall the wifi drivers
Reboot
Reinstall just the wifi drivers


Afterwards, I can connect to the office wifi... and hostednetwork works! Go figure :-/