Hi all,
knowning that there are already a lot of posts concerning above message, I have to write an additional one as I could not find a solution on the web yet.
Situation:
Windows Server 2008 forest including empty root and two child domains, one child domain does have SCCM SP1 (central primary site WND) installed on W2k8 x64 machine including WSUS 3.0 SP1 => everything is working fine.
Second child domain also contains a SCCM SP1 server (primary site HUN) running on W2k8 x64 and is defined as child site of central site WND => everything is working fine too - except Software Updates.
WSUS 3.0 SP1 installed on both SCCM servers by creating additional web site (not using "defautl web site") and configured ports 8530 and 8531 (SSL not used!). No proxy necessary/used. All WSUS 3.0 requirements for W2k8 are installed (IIS roles)
Error:
SMS_WSUS_CONFIGURATION_MANAGER - MessageID 6600:
SMS WSUS Configuration Manager failed to configure upstream server settings on WSUS Server "xxxx0003".
Possible cause: WSUS Server version 3.0 SP1 and above is not installed or cannot be contacted.
Solution: Verify that the WSUS Server version 3.0 SP1 or greater is installed. Verify that the IIS ports configured in SMS are same as those configured on the WSUS IIS website.
wsusutil checkhealth =>OK
downloading updates from WSUS at central site (SUSDB and WSUS folder equal in size) =>OK
wsus admin console able to connect and configuration possible => OK
IIS ports configured within SMS are equal to those configured for WSUS website
SCCM config (using Configuration Manager Console) does look correct - ConfigMgr Software Update Point role properties and Software Update Point Component properties
wcm.log does report an error: (SCCM Log files at the end.)
"The request failed with HTTP status 503: Service Unavailable"
IIS log files of both websites (default web site and WSUS Administration website) do not show any errors.
Questions:
What else should I look at? (registyr, SUSDB content,..)
What exactly does happen during the attempt to configure the upstream server by the SMS_WSUS_Configuration_Manager component? I guess a SMS process tries to contact a webservice - would it be possible to debug in more detail ?
And finally - Who does know the solution ? 
wcm.log:
Found WSUS Admin dll of assembly version Microsoft.UpdateServices.Administration, Version=3.0.6000.273, Major Version = 0x30000, Minor Version = 0x17700111 SMS_WSUS_CONFIGURATION_MANAGER 16.07.2008 12:49:47 4468 (0x1174)
Found WSUS Admin dll of assembly version Microsoft.UpdateServices.Administration, Version=3.1.6001.1, Major Version = 0x30001, Minor Version = 0x17710001 SMS_WSUS_CONFIGURATION_MANAGER 16.07.2008 12:49:47 4468 (0x1174)
The installed WSUS build has the valid and supported WSUS Administration DLL assembly version (3.1.6001.65) SMS_WSUS_CONFIGURATION_MANAGER 16.07.2008 12:49:47 4468 (0x1174)
System.Net.WebException: The request failed with HTTP status 503: Service Unavailable.~~ at Microsoft.UpdateServices.Administration.AdminProxy.CreateUpdateServer(Object[] args)~~ at Microsoft.UpdateServices.Administration.AdminProxy.GetUpdateServer(String serverName, Boolean useSecureConnection, Int32 portNumber)~~ at Microsoft.SystemsManagementServer.WSUS.WSUSServer.ConnectToWSUSServer(String ServerName, Boolean UseSSL, Int32 PortNumber) SMS_WSUS_CONFIGURATION_MANAGER 16.07.2008 12:49:47 4468 (0x1174)
Remote configuration failed on WSUS Server. SMS_WSUS_CONFIGURATION_MANAGER 16.07.2008 12:49:47 4468 (0x1174)
STATMSG: ID=6600 SEV=E LEV=M SOURCE="SMS Server" COMP="SMS_WSUS_CONFIGURATION_MANAGER" SYS=xxxx0003 SITE=HUN PID=2424 TID=4468 GMTDATE=Mi Jul 16 10:49:47.758 2008 ISTR0="xxxx0003" ISTR1="" ISTR2="" ISTR3="" ISTR4="" ISTR5="" ISTR6="" ISTR7="" ISTR8="" ISTR9="" NUMATTRS=0 SMS_WSUS_CONFIGURATION_MANAGER 16.07.2008 12:49:47 4468 (0x1174)
Waiting for changes for 59 minutes SMS_WSUS_CONFIGURATION_MANAGER 16.07.2008 12:49:47 4468 (0x1174)
wsusctrl.log (looks fine to me - is able to connect to local WSUS !):
SMS_EXECUTIVE started SMS_WSUS_CONTROL_MANAGER as thread ID 6156 (0x180C). SMS_WSUS_CONTROL_MANAGER 16.07.2008 12:04:01 2732 (0x0AAC)
This is a WSUS Role as WSUS registry key exists. SMS_WSUS_CONTROL_MANAGER 16.07.2008 12:04:01 6156 (0x180C)
Found WSUS Admin dll of assembly version Microsoft.UpdateServices.Administration, Version=3.0.6000.273, Major Version = 0x30000, Minor Version = 0x17700111 SMS_WSUS_CONTROL_MANAGER 16.07.2008 12:04:01 6156 (0x180C)
Found WSUS Admin dll of assembly version Microsoft.UpdateServices.Administration, Version=3.1.6001.1, Major Version = 0x30001, Minor Version = 0x17710001 SMS_WSUS_CONTROL_MANAGER 16.07.2008 12:04:01 6156 (0x180C)
The installed WSUS build has the valid and supported WSUS Administration DLL assembly version (3.1.6001.65) SMS_WSUS_CONTROL_MANAGER 16.07.2008 12:04:01 6156 (0x180C)
Successfully connected to local WSUS server SMS_WSUS_CONTROL_MANAGER 16.07.2008 12:04:01 6156 (0x180C)
Local WSUS Server Proxy settings are correctly configured as Proxy Name and Proxy Port 80 SMS_WSUS_CONTROL_MANAGER 16.07.2008 12:04:01 6156 (0x180C)
Waiting for changes for 0 minutes SMS_WSUS_CONTROL_MANAGER 16.07.2008 12:04:01 6156 (0x180C)
Timed Out... SMS_WSUS_CONTROL_MANAGER 16.07.2008 12:04:01 6156 (0x180C)
Found WSUS Admin dll of assembly version Microsoft.UpdateServices.Administration, Version=3.0.6000.273, Major Version = 0x30000, Minor Version = 0x17700111 SMS_WSUS_CONTROL_MANAGER 16.07.2008 12:04:01 6156 (0x180C)
Found WSUS Admin dll of assembly version Microsoft.UpdateServices.Administration, Version=3.1.6001.1, Major Version = 0x30001, Minor Version = 0x17710001 SMS_WSUS_CONTROL_MANAGER 16.07.2008 12:04:01 6156 (0x180C)
The installed WSUS build has the valid and supported WSUS Administration DLL assembly version (3.1.6001.65) SMS_WSUS_CONTROL_MANAGER 16.07.2008 12:04:01 6156 (0x180C)
Successfully connected to local WSUS server SMS_WSUS_CONTROL_MANAGER 16.07.2008 12:04:01 6156 (0x180C)
Local WSUS Server Proxy settings are correctly configured as Proxy Name and Proxy Port 80 SMS_WSUS_CONTROL_MANAGER 16.07.2008 12:04:01 6156 (0x180C)
Successfully connected to local WSUS server SMS_WSUS_CONTROL_MANAGER 16.07.2008 12:04:01 6156 (0x180C)
There are no unhealthy WSUS Server components on WSUS Server xxxx0003 SMS_WSUS_CONTROL_MANAGER 16.07.2008 12:04:01 6156 (0x180C)
Successfully checked database connection on WSUS server xxxx0003 SMS_WSUS_CONTROL_MANAGER 16.07.2008 12:04:02 6156 (0x180C)
Waiting for changes for 57 minutes SMS_WSUS_CONTROL_MANAGER 16.07.2008 12:04:02 6156 (0x180C)
wsyncmgr.log (as a result of being not able to configure upstream server I guess):
STATMSG: ID=6701 SEV=I LEV=M SOURCE="SMS Server" COMP="SMS_WSUS_SYNC_MANAGER" SYS=xxxx0003 SITE=HUN PID=2424 TID=4476 GMTDATE=Mi Jul 16 10:03:51.481 2008 ISTR0="" ISTR1="" ISTR2="" ISTR3="" ISTR4="" ISTR5="" ISTR6="" ISTR7="" ISTR8="" ISTR9="" NUMATTRS=0 SMS_WSUS_SYNC_MANAGER 16.07.2008 12:03:51 4476 (0x117C)
Sync failed: WSUS server not configured. Source: CWSyncMgr:
oSync SMS_WSUS_SYNC_MANAGER 16.07.2008 12:08:51 4476 (0x117C)
STATMSG: ID=6703 SEV=E LEV=M SOURCE="SMS Server" COMP="SMS_WSUS_SYNC_MANAGER" SYS=xxxx0003 SITE=HUN PID=2424 TID=4476 GMTDATE=Mi Jul 16 10:08:51.636 2008 ISTR0="CWSyncMgr:oSync" ISTR1="WSUS server not configured" ISTR2="" ISTR3="" ISTR4="" ISTR5="" ISTR6="" ISTR7="" ISTR8="" ISTR9="" NUMATTRS=0 SMS_WSUS_SYNC_MANAGER 16.07.2008 12:08:51 4476 (0x117C)