SSP or new Site not reachable from IE8 on App Server:

I couldn't understand what was going wrong with new SP site which i created. When I browse with IE8 on App Server it throws a http error 401.1 (You are not authorized to view this page).. Even with local Admin or MOSS Farm admin(same in my case) it was not authenicating users

Finally found this on technet. It says it is to do with one update.

http://social.technet.microsoft.com/Forums/en-US/sharepointadmin/thread/a8ec1c91-c0d2-42ca-a222-35e7f0cecf26



If you are not able to access the site only on the server, then this is probably related to one of the updates which went out recently. I am not sure which one, but I had the same problem and could fix it by making the following registry change:
Click Start, click Run, type regedit, and then click OK.
In Registry Editor, locate and then click the following registry key: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa
Right-click Lsa, point to New, and then click DWORD Value.
Type DisableLoopbackCheck, and then press ENTER.
Right-click DisableLoopbackCheck, and then click Modify.
In the Value data box, type 1, and then click OK. Quit Registry Editor, and then restart your computer.