Hello

I am having a big problem with my forum.
When trying to log in, it fails with the message "Invalid password!".
When trying to log in with the same password, it accepts, HOWEVER, when loading a new page, it just logs me out.
Any tips? Can't list my mods because I can't access the Admin panel.
SMF version: 2.0 RC5
Browser: IE (no other's tested)