I just recently ran into this problem. But it wasn't always the case.

When I first got my N800 I upgraded the OS and everything and it was working fine. I have multiple GMAIL accounts and for several months now the dialog box with the selection of all my accounts would pop the same would happen on MySpace where I also have multiple accounts (personal, band, etc)

Well first, the dialog stopped popping up on MySpace and now I have to write in the email and password every time, but at Gmail I have the same issue as you. The dialog box pops up I select the account but nothing happens, after typing in the username the password shows up.

Has anyone fixed this? I also need help!