Today I tried the use the Slacker website again and received the following message:
Slacker Personal Radio
Is not available in your area.
Slacker Personal Radio is currently available in the United States.
If you are getting this message and are in the United States please use the feedback form to tell us where you are located and the name of your ISP.
I have now written off Slacker. Bye Slacker. You are well named.