Error in login&logout

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I can't logout and login my site. I get these errors:

Warning: array_merge() [function.array-merge]: Argument #1 is not an array in /root/updates/concrete5.5.2/concrete/libraries/events.php on line 163

Warning: Cannot modify header information - headers already sent by (output started at /root/updates/concrete5.5.2/concrete/libraries/events.php:163) in /root/packages/vanilla_forums/models/user_logout.php on line 8

Warning: Cannot modify header information - headers already sent by (output started at /root/updates/concrete5.5.2/concrete/libraries/events.php:163) in /root/updates/concrete5.5.2/concrete/models/user.php on line 247


Thank You!

marticps