Window 2003 Server – “Service Unavailable” on IIS webpage

All of a sudden the web applications installed on Windows 2003 Server with IIS 6.0 stopped working.

• Observed that IIS is running and all the windows services related to installed web application is up and running. 
• Restarting IIS and web application related services was of no help. 
• Enabling Isolation Mode (Web Sites Properties -> Services -> Isolation Mode -> Run WWW service in IIS 5.0 isolation mode).

Later on identified that Windows security updates installed on Dec 9th 2009 have caused the problem.

Solution:
Initially uninstalling the following Windows security updates and restarting the machine have fixed the issue.

KB976325
KB973904
KB973917
KB971737
KB974318
KB974392

Exploring further could help us narrow down that by just removing Windows Update KB973917, the 'Service Unavailable' issue will be resolved. However while removing it says KB974392 may not work properly. On resrting the machine IIS & WebApplications are working properly.