The Microsoft KB963027 Update, released on April 14th, 2009 breaks NTLM logins from the Small Business Server to its own http://companyweb server, among other things. To read more about this bug, please see Microsoft’s support page: http://support.microsoft.com/kb/963027. Logins may also break from Vista clients. I have tested Microsoft’s “Method 2” fix, and it does work, however I found that there was some vague language I would like to clarify for you. I have prepared the following how-to to complement Microsoft’s:

How to fix the inability to login to companyweb on a SBS 2008 machine after the 963027 update

In Notepad, as Administrator:

• open c:\windows\system32\drivers\etc\hosts
• add:
  • [your ipv6 address] localhost 
  • [your ipv6 address] companyweb 
  • [your ipv6 address] [your external DNS name, remote.domain.com]

In Regedit as Administrator:

• open HKLM\SYSTEM\CurrentControlSet\Control\LSA\MSV1_0\
• Right-click MSV1_0, point to New, and then click Multi-String Value.
• Rename it to BackConnectionHostNames
• Right-click BackConnectionHostNames, and then click Modify.
• In the Value data box, type "companyweb", hit [enter]
• Type in "[your external DNS name]"
• Make sure you have no extra lines

Restart IIS, or reboot server