When I try to logout as Admin I get the following error messages and I don't get logged out.

Warning: Cannot modify header information - headers already sent by (output started at /home/alkha4/public_html/blog/b2evocore/_class_dataobjectcache.php:439) in /home/alkha4/public_html/blog/b2evocore/_functions_users.php on line 173

Warning: Cannot modify header information - headers already sent by (output started at /home/alkha4/public_html/blog/b2evocore/_class_dataobjectcache.php:439) in /home/alkha4/public_html/blog/b2evocore/_functions_users.php on line 174

Warning: Cannot modify header information - headers already sent by (output started at /home/alkha4/public_html/blog/b2evocore/_class_dataobjectcache.php:439) in /home/alkha4/public_html/blog/b2evocore/_functions_users.php on line 175

Warning: Cannot modify header information - headers already sent by (output started at /home/alkha4/public_html/blog/b2evocore/_class_dataobjectcache.php:439) in /home/alkha4/public_html/blog/b2evocore/_functions_users.php on line 177

Warning: Cannot modify header information - headers already sent by (output started at /home/alkha4/public_html/blog/b2evocore/_class_dataobjectcache.php:439) in /home/alkha4/public_html/blog/b2evocore/_functions_users.php on line 178

Warning: Cannot modify header information - headers already sent by (output started at /home/alkha4/public_html/blog/b2evocore/_class_dataobjectcache.php:439) in /home/alkha4/public_html/blog/b2evocore/_functions_users.php on line 179

Warning: Cannot modify header information - headers already sent by (output started at /home/alkha4/public_html/blog/b2evocore/_class_dataobjectcache.php:439) in /home/alkha4/public_html/blog/htsrv/login.php on line 67

Warning: Cannot modify header information - headers already sent by (output started at /home/alkha4/public_html/blog/b2evocore/_class_dataobjectcache.php:439) in /home/alkha4/public_html/blog/htsrv/login.php on line 69

Warning: Cannot modify header information - headers already sent by (output started at /home/alkha4/public_html/blog/b2evocore/_class_dataobjectcache.php:439) in /home/alkha4/public_html/blog/htsrv/login.php on line 71

Warning: Cannot modify header information - headers already sent by (output started at /home/alkha4/public_html/blog/b2evocore/_class_dataobjectcache.php:439) in /home/alkha4/public_html/blog/htsrv/login.php on line 73

Warning: Cannot modify header information - headers already sent by (output started at /home/alkha4/public_html/blog/b2evocore/_class_dataobjectcache.php:439) in /home/alkha4/public_html/blog/htsrv/login.php on line 81

I also get similar messages about the header when I do other things

Can anyone please help :?: