Hi Andy,
We don't have anything that prevents users from signing in, there is a setting that prevents new users from registering but nothing that prevents existing users from signing in. If you don't see a link to sign in that might be a skinning issue but you can navigate to yoursiteroot/Secure/Login.aspx to sign in.
If that doesn't help please clarify what you did and what you mean by "Locked Out"
Hope that helps,
Joe