WSUS SP1 Readme is updated (on 21st June 2006) with known issues once you apply WSUS SP1.
Readme for WSUS Service Pack 1: This document describes known issues affecting Windows Server Update Services Service Pack 1 (WSUS SP1).
New Known Issues:
Issue 6: If you are using a proxy server, the SP1 upgrade may clear the proxy configuration username and password
Issue 7: How to recover from a failed upgrade to restore your WSUS server to a consistent state and then retry the upgrade.
Issue 8: WSUS SP1 upgrade can fail in some cases when the WMSDE database has been migrated
Issue 9: WSUS SP1 is not updating WSUS servers which are setup using remote SQL deployments
Issue 10: Changing the computer name prior to upgrading to WSUS SP1 can cause the upgrade to fail
Direct Link: http://download.microsoft.com/download/7/d/c/7dce8ed3-8d44-421f-902c-95391577ecb5/ReadMe.htm
Got caught with issue 10
Issue 10: Changing the computer name prior to upgrading to WSUS SP1 can cause the upgrade to fail
and didnt notice it but instead ran the setup again!
(overwritten the backup DB)
so i had no way to recover DB… if anyone have problem, Dont RUN setup for SP1 again before copying the backed up DB to other location!!!!