Try the following:

1 - Start > Control Panel > Network and Internet Connections (if in category view) > Network Connections > right-click the icon for the connection you use > select Repair.

2 - Start SDC > File menu > make sure "Work Offline" is not selected > if you still do not logon to server, try changing servers by going to "Tools menu > Settings > Internet category > change the server in list > OK.

If these fail, and you can access the internet with another browser, something must be amiss with your information.