Comment 10 for bug 505323

It seems that in the latest version (natty) you cannot use tab to select the language selection or the login options (useful if you nuke your xconfig file, have limited graphics support and your mouse doesn't seem to be working otherwise you can't login because unity is set to default and won't run). If however you hit Alt + F6 it will take focus away from the top panel and give it to the bottom panel allowing you to tab between the options, hit the key combo again and your back on the top panel. Not sure if this is a feature or will solve your issue.