Dashboard feed showing “forbidden” error

I’m getting the following error message on my Dashboard page:

Forbidden

You don’t have permission to access /wp-admin/index-extra.php on this server.

Apache/1.3.33 Server at mydomain.net Port 80

Presumably a permissions problem? If so, how do I fix it? And what else should I check to make sure it’s not broken either?

I’ve been experimenting with the K2 theme so presumably it’s something to do with that.