Apparently there's a few problems with the ST585v6 and wireless performance. I've also installed a few WG111 adapters for people and wasn't overly impressed with their performance either (various different makes and models of routers)
The only thing of any potential use that's coming up when searching the Be forum, is a mismatch between the "preamble" setting on the router and the wifi adapter, and someone on the Be forum has advised to check your preamble settings in the Advanced Settings page for the network adapter - which you can get from going into the Netgear software and clicking "Advanced Settings".
I don't have a WG111 so can't test this out, but apparently you can choose a Preamble type of Long, Short or Auto. Short preamble may give better performance, Long may give a more reliable connection.
Let us know if you have any joy