I've applied a small patch I wrote this weekend that should now allow everyone to login from multiple browsers and/or multiple servers. Consider this the "test phase" -- let me know if you run into any problems.
Note that I'm aware of one issue in which you log in, then going back to the front page suddenly you no longer appear to be logged in. If this happens to you, before logging back in try to simply "shift-reload" to force your browser to load a current copy of the page. That should reveal that you're actually still logged in.
Anyway, please try logging in with multiple browsers and let me know how this works. :)