warning: array_keys() [function.array-keys]?

Hi,

I'm trying to install 5.1 in a subdomain. The installation script runs through fine but when I go to the index.php page I get 'Access denied' and a load of errors like this.

warning: array_keys() [function.array-keys]: The first argument should be an array in /home/example/public_html/somesubdomain/modules/user/user.module on line 361.

warning: implode() [function.implode]: Bad arguments. in /home/example/public_html/somesubdomain/modules/user/user.module on line 361.

I've also tried to install Drupal through my hosts' Fantastico installation script, but we get the same problem. Again, this is trying to install Drupal in a subdomain.

Any ideas?

:) M.