virtual serv and php flags

I have apache 2 with many VS like this

<VirtualHost 212.160.183.129>
ServerName www.aa.bb.pl
ServerAlias aa.bb.pl *.aa.bb.pl
DocumentRoot /home/xx/public_html
ServerAdmin xx@bb.pl
</VirtualHost>

and everything works OK until
I've changed one of virtual servers to this

<VirtualHost 212.160.183.129>
ServerName www.aa.bb.pl
ServerAlias aa.bb.pl *.aa.bb.pl
DocumentRoot /home/xx/public_html
ServerAdmin xx@bb.pl
php_admin_value open_basedir /home/xx/public_html
php_admin_value safe_mode off
</VirtualHost>

and after this every php page on server has problems -
randomly i see error like bellow


Warning: Unknown(): open_basedir restriction in effect.
File(/home/kot/public_html/glowna.php) is not within the allowed path(s):
(/home/lo/public_html) in Unknown on line 0

Warning: Unknown(/home/kot/public_html/glowna.php): failed to open stream:
Operation not permitted in Unknown on line 0

Warning: (null)(): Failed opening '/home/kot/public_html/glowna.php' for
inclusion (include_path='.:/usr/share/php') in Unknown on line 0