I have been having the same problem. When I try to register I get the same message, and cannot receive updates. I have Internet Explorer 7. I rang tech supprt, they asked me to re-install the software (originally from a CD) - this did not work.
Go to IE7 Tools/Internet Options/Advanced and click Reset. Then click Apply and OK. Close and reopen IE7 and then re-enable all the add-ons under Tools/Manage Add-ons.
Also check your system clock for accuracy both time and timezone-wise.
Moved this to your own thread.
Please post what operating system & service pack you are using, how you connect to the internet, if you are behind any proxy or commercial firewall and if you have any other protection software installed.