Hi,
Let me put your mind at rest, you are seeing this error as the certificate for the cpanel secure access is a self signed one, however this does not mean its any less secure.
You can safely continue passed the errors that some browsers will give you. If you do not wish to see these errors you can access the cpanel via the non secure port
http://www.yourdomain.com:2082 but we always recommend accessing your cpanel via the secure port.
Let me know if I can help with anything else.
Dream-hosting.co.uk Admin