Login and some other issues

Im using 1.5.6 on a webhost server
I just installed it, and I keep seeing this error.
Plus when I try to login in nothing happens.
The sessions test page works. I dont have access to php.ini.

It does work though when I login thru the setup page.
I get this error all around Gallery:

Warning: set_time_limit() has been disabled for security reasons in /home/uno500/public_html/fotoo/init.php on line 68

Allso when I try to add a new user i get this message:

Warning: Cannot modify header information - headers already sent by (output started at /home/uno500/public_html/fotoo/init.php:68) in /home/uno500/public_html/fotoo/manage_users.php on line 36