wp-login.php and wp-admin/ bouncing back and forth

I’ve just set up a few WP blogs for my team at work, and when any of us log in to the admin console for our blog, we get taken to the wp-login.php page as normal.

Once we enter ID & PW and click the login button, the browser goes into a loop between wp-admin/ and ‘wp-login.php?redirect_to=/Keith.Murray/wp-admin/index.php’

If I stop the browser, and key-in the wp-admin/ URL it takes me to the admin page. Not a complete disaster for me, but some of my less technical users are getting frazzled.