Re:HELP- changed from neat.css to geoo-light.css and cannot login anymore-even as admin...
Did you try using /tiki-login_scr.php? Also try clearing your Smarty cache in the templates_c directory.
Just a tip: never change your theme on a site-wise scale. Instead create a test user and assign a new style to that account. If things get messed up you can then still go back into Tiki as the 'admin' user under the old theme.
Regards,
Pat.