Do you have OpenSSL plugin active, as it is needed in win XP? (It is listed in VersionInfo) Could you make
Network log for core ang gg with all options and see if there are any additional info? (Console plugin could be usefull to just look them up in real time).
GG plugin was changed to force SSL Connection and that with updates to libgadu library result in disconnection if it cannot be established. Before that even when option to make secured connection was checked in options, then in case of fail, plugin was connecting with unsecured connection probably silently (not sure if there was popup error, or just single entry in log)