4
I had the same problem, even after I did the things recommended by gediminasbyt.
If those suggestions don't work. Check your mainfile.php. At line 39 you should see something like:
define('XOOPS_URL', 'http://yoursite.com');
add the www.:
define('XOOPS_URL', 'http://www.yoursite.com');
That fixed it for me...
Beagle