SBS CompanyWeb Sharepoint HTTP 403 error - Access Forbidden IP Address not within range

Hi

Issue:
Getting the 403 error and IP not within range when trying to access the the companyweb from the server as well as all clients (Vista).

Access to the web and email appears to be ok at this point for server and desktops.

Have checked all the settings that obviously restrict access but nothing obvious stands out as well as stopped and restarted the site.

Also, Symantec's Backup Exec v12 has suddenly started demanding a password when 3 days before it did not.  Of course the Sql instance will not start without that password.

Background:
Not sure whether its related to the patch MS08-067 released Tues 21st Oct or not.  Why that's so is that the patch did not install despite being downloaded to the server, although it did install on the desktops.  Issues with the companyweb were first reported by users on the desktops.  The patch was manually applied to the server after the reports from the desktop users.

As well, I've just (this week)  taken over this site from another service provider so I have no personal experience of how SBS and the other app s were installed etc.

Any ideas?

thanks