Works on NT 5.0, but with header/cookie issue

[mello2n]

Hi,
I have it working on an NT 5.0 / IIS 5 webserver.
However, when logging out I get the following errors:

Cannot add header information - headers already sent by (output started at D:\Inetpub\....path....\includes\shared.lib.php:722) in D:\Inetpub\....path....\includes\shared.lib.php on line 183

Line 183 in the shared.lib.php file is

   function logOut(){
[line 183]      setcookie("session", "", 0);

      return true;
   }

Solutions anyone?

Thanks in advance. I appreciate it.