404 Error when activating buddypress account

Hello,

Just joined, so apologies if this doesn't classify as advanced.

I have Buddypress installed and ready to go, but I just cant get the login link to work after activating a new account.

Once you sign up, you get the confirmation email, click on that, and that takes you to the confirmation screen where you can go to your site or login.

The login link goes to the standard wordpress login (/wp-login.php) which is suppose to redirect to the home page where buddypress is... e.g...

http://mydomain.com/wp-login.php?redirect_to=http://mydomain.com

That gives me a 404 error.

But, if I click on the buddypress bar at the top to login, it takes me to
http://mydomain.com/wp-login.php?redirect_to=http%3A%2F%2Fmydomain.com which works fine.

Anyone have an idea what to do?

Thanks!

George