Forums / Cotonti / Support / Login issue

After i login i get a blank page with "1" on it and nothing else.
In the system log i have this:

88 2009-03-14 18:45 83.108.19.36 Users Log in failed, user : sigbha - /users.php?m=auth&a=check
87 2009-03-14 15:31 81.191.3.166 kakeman Users Log in failed, user : - /users.php?m=auth&a=check
86 2009-03-14 10:44 77.18.68.143 KDS86 Users Log in failed, user : - /users.php?m=auth&a=check

What could be wrong?