Admin login loop

Hi there!
i’ve installed wp 2 days ago, installed new theme and could login as admin without any problems, so i think i just logged in once.
Since then i can not login on my admin account, i didnt set any others yet.
When i login the site reloads. when i enter a wrong password it tells me its wrong, i can request a new one “lost password”, but trying to login just reloads the page. and the old one gets “wrong password”.
there are may suggestions for this problem out there but none seems to work, and many seem to have the same issue.
I’ve cleared cookies and deleted plugins folder nothing works.

The OS has nothing to do with it but i’m on
OSX and WinXP, firefox 3.0.7 and safari 3.2.1