E-mail problems

[Titanium]

Hi, i have just installed your very nice script to my webserver (www.aeger.se/myred/home.php) and everything works great, exept the mail sending. When a user registrates or u use the "contact" form i just get this message "Warning: Unknown error in D:\internet\domains\aeger.se\www\myred\contact.php on line 39"...

I'm using Microsoft-IIS/5.0 and PHP Version 4.1.1.

Please help me with this problem, and btw very good work!