1.0-alpha3-nightly.build.2747 on Windows Vista fully updated
This morning when logging in to GMail talk via a Jabber account link using both builds 2743 and 2747 (after updating), I got a window pop up from Sip-Communicator which did not have any text in it and composed mainly of the title bar. The title begins with J (it says 'Jabber authentication on the bar at the bottom of the taskbar) but I cannot read beyond that as the window is too small and the minimise and close buttons etc. take up the space. The window cannot be re-sized. When I closed the window, I was not logged in. I went to the Edit account details and noticed that the password had gone (it is set as 'remember') and re-entered it and it logged in okay.
After this had happened, I thought I would add as a GoogleTalk account (not Jabber) another GMail login that I have. I have the same issue with this (the small empty pop up window and no log in). When I go to edit the account details, however, the password is there and it continues not to log in. Every time I try and change the status the empty pop up appears. Right now, I have the 'Sign In' window of the Account Registration Wizard window open, the About SIP Communicator window open and the empty Jabber Authentication window open, none of which can be closed in any way. I'll have to kill the program and re-start it.