[Tigga]

Oh, thank you for pointing that out. I guess I changed the template so long ago on my site and forgot that would be necessary.

To fix it, edit your head_newpm template and look for:
window.location="private.php?s=$session[sessionhash]";

Change that to:
window.location="$bburl/private.php?s=$session[sessionhash]";

That should work, but if it doesn't replace the $bburl there with the url to your forums. Sorry about that and thank you for pointing it out.