vBulletin 5.1 - Login and Logout error

[Jan Grohmann]

Dears,
I´m looking for help. I have got problem with login and logout in vBulletin 5.1.

If I would like logout from my account, result is error page:

Debug: Error
strpos(): Empty needle
occurred in file /hosting/www/armadninoviny.cz/www/forum/includes/vb5/cookie.php on line 85
Trace

• Function handleError in file line
• Function strpos in file /hosting/www/armadninoviny.cz/www/forum/includes/vb5/cookie.php line 85
• Function deleteAll in file /hosting/www/armadninoviny.cz/www/forum/includes/vb5/frontend/controller/auth.php line 185
• Function actionLogout in file line
• Function call_user_func_array in file /hosting/www/armadninoviny.cz/www/forum/index.php line 72

I have (and also testers) sometimes problems with login. I would try login with right username and password, but result is none. I can´t login and even ther is no "error" message or page. Just no response from forum.

Yep, I re-instal vbulletin 5.1 5x times and yep, I delete all cookies and history in browser. Same results are in Firefox an Explorer.

I will be glad for any help, I´m little bit frustrated with this software.