ISA and Domains

Problem:
OS on Server: Window 2000 SBE with Exchange Server 2000 and ISA Server 2000 setup.

LocalDomain: .com
Email addresses: @.com
Web Site Hosted by a 3rd Party: www..com

Because of the setup as describrd above, ISA Firewall pops up a Firewall Logon Dialog Box but still refuses to allow access to the hosted web address.

Things tried so far:
1. Add ISA Server IP Address as Gateway, it worked initially but has since stopped due to change over to DSL.
2. Auto-download the website to the cache via ISA Server, seemed to work but not anymore.

Any ideas would be greatly appreciated.