Problem with user authentication

[eluser]elof[/eluser]
Oh lord... just solved it. The issue was... wait for it... the <form>'s action attribute.

Replacing <form action="/community/login" method="POST"> with <form action="http://www.example.com/community/login" method="POST"> fixed it. I've no idea what was the problem - a local URL vs a full URL? Why would that cause something like that? I'd be glad if someone could enlighten me on this issue, because I've seriously no idea why that caused a problem in the first place.

Thanks to everyone who replied to the thread, I really appreciate it. You'll likely be hearing from me again if (... when) I run into more trouble.