Mike, I just tried your Kearney Vac site, and tried out the link and got an error. However, the error seems to be a 403 Forbidden error (that's what shows in the tab on Firefox). The 404 is from trying to access an error document.
Do you maybe have your htaccess on your michaelstreeter.com site set up to only allow (or deny) access from certain IP addresses? I found this link that talks about how to allow/deny requests.