IIs 503 Error

After I performed my last windows update, all my web pages began displaying the "Service Unavailable" error in the web browser. IIS(6) shows that the default application pool is not running and encountered an error(503 according to the logs). I tried numerous things including the link below and uninstalling .NET and reinstalling the 2.0 redeployment package....i was certain this would have fixed the problem. I've restarted the server and IIs several times. I even went back and uninstalled all the updates that took place yesterday(when this started). No affect so I just reinstalled them.

http://blogs.msdn.com/david.wang/archive/2005/09/23/HOWTO_Diagnose_one_cause_of_503_Service_Unavailable_on_IIS6.aspx

The logs don't tell me much, and i've ran the script to put IIs in 32 bit mode as well. I'm running Windows Server 2003. Has anybody ran into this problem and found a solution? Thanks in advance.

What's the complete error text? If you're using IE you may need to turn off the "show friendly http errors" setting to see the complete error message.

I can't provide the error details(not that it gave much) because we went ahead and recovered a backup to correct the problem. However, I would like to discover the underlying problem due to the fact that we are afraid to allow the server to perform any updates.