does leaving your settings to connect automatically to any known wifi and 3g not work? perhaps you've left it connecting to any wifi and get html secure password access points taking priority over 3g connection and not giving you access?
i vaguely remember seeing a script someone wrote on here that would be used for connecting to public wifi's, but would ping an ip to test the connection, therefore not wasting time being connected to hotspots which require a password after connecting, perhaps this script could be modified to suit your settings?