Error when signing up

Hey. Just opened a wpmu site with pick-a-site and "sites". Users can choose between 3 domains. However, I get this error on signup:

Warning: extract() [function.extract]: First argument should be an array in /dir/wp-signup.php on line 334

Line 333 and 334 is:

$result = wpmu_validate_blog_signup($_POST['blogname'], $_POST['blog_title']);
extract($result);

There is no email sent. I know for a fact the email service works. I'm running Xpert mailer plugin.

Anyone know what the problem might be? I would appreciate any help.