So you are referring to
Issue 1215: IP settings for WiFi networks?
Looks like this has been an issue since 2008 and still hasn't been addressed with the release of Gingerbread. IP Manager is listed as a solution (link above).
Evidently, another app, WiFi Static was created to address this issue as well:
http://www.appbrain.com/app/wifi-sta...oc.wifi.statIc
My environment doesn't require a solution for these issues so I am unable to confirm or deny. Others that have this requirement say they work. YMMV.