It tries to post back to itself, but referenced as "./" not "./index.php" - you might check your apache config to see that index.php is listed on your DirectoryIndex line. (Where index.html, index.htm, etc are listed as valid index pages)
Hmm...Does it say anything in Apache's error log? It should mention what it is trying to access that's showing up 404.You could paste the output here if you want, too.
Edit the post line in skins/default/templates/login.html from:<form name="form" action="./" method="post">to<form name="form" action="./index.php" method="post">This will allow you to actually login.Next, in the index.php file, edit this line:// set session related variables$COMM_PATH = sprintf('./?_auth=%s&_task=%s', $sess_auth, $_task);to read// set session related variables$COMM_PATH = sprintf('./index.php?_auth=%s&_task=%s', $sess_auth, $_task);This will allow the rest of the functions to work.You will also need to edit the "action" lines in the following files:program/steps/settings/func.inc (this is for preferences)program/steps/addressbook/edit.inc (this is for the address book obviously)program/steps/mail/compose.inc (this is for attachments while composing messages)Just change the "./" to "./index.php"