hacking sf

I have just downloaded the sourceforge source from sf.net and I am trying to hack it witohut much luck. The login mechanism just doesn't seem to work. It uses manually set cookies instead of inbuild session stuff and I never got it to work like that. I don't know exatcly why but the cookie just never gets set even tho the function is called and there are no complaints. I have put a tarball of the code on my site: http://dev.genestate.com/projects/sf.tar.gz Relevant code is in: include/session.php account/login.php include/user.php The login file calls session_login_valid() which calls various functions including the set_cookie. Please can someone give me a hint? cheers