Are you running Version 1 or version 2 of the WG111? ( V1 hardware SN starts with WG16 or WG72 or 130. it is also usually marked on its box as "Tivo Compatible". v2 hardware SN usually starts with WG41 or 165. anything else and you have not a wg111, but a wg111-u or -t with their speedboost or rangemax hardware.)
http://kbserver.netgear.com/products/wg111.asp
I am running version 1 on Vista RC1. It works with the stock Netgear drivers at bootup, either with Wireless Zero (windows wireless client) or with the netgear client.
HOWEVER... if I lose the signal or insert another USB device like my flash drive, it dumps the connection and I have to reboot to get it working again (unlike XP, Vista does not have a "Repair" option, but a much less informative "diagnose" option that is still not yet working well in RC1.)
Also, maybe it is your motherboard? do you have their most recent or vista-qualified drivers?
Most of the other websites I visit say that the most current version of WG111 v2's drivers are vista-certified, but They won't work with my older v1.