I'm fillling in the fields exactly like they are on my desktop install of Pidgin (which works). I'm just using 'xxxx' in the 'screenname' field and 'gmail.com' in the domain field. adding '@gmail.com' to the screenname results in the screenname changing back to just 'xxxx' and the domain becoming '@gmail.com@gmail.com' the next time I go in to edit the account settings.

Thanks for the ideas though. Got any more?