Hi dave,
Have your friend delete any invitations he's received in his email. You should also delete the pending invitation in your members list.
Visit your friends profile and click the invite to country club button at the top of the profile. After you do this you can leave a message on your friend's wall telling him to check his email.
Once your friend receives the invitation in his email he should log into WGT first and then click the confirmation link in the email. That will accept the invitation and that's all you have to do.
If your friend is not receiving the invitation he will need to double-check the email listed on his account. It's also possible that the email is being forwarded to a spam or junk folder, so have him check there as well.
Good Luck =)