IIS 6 Errors

[Sargera]

On a few Websites, completely random, I get "Service Unavailable" errors reported from IIS 6. This is being caused by a permissions change (for the user associated with the website, i.e. IUSR_paul), which no one has been messing with. How can I prevent this from happening and/or what is causing this?

Note: Server is running Windows Server 2003, Standard Edition and Plesk for Windows v7.0.1.  Additionally, by referring to the Websites, I am referring to the domains/Websites associated with a user account, which report this error when you go to the Website.

[quasi-modo]

A 403 is what you should get when you do not have access to something

You are not authorized to view this page
You might not have permission to view this directory or page using the credentials you supplied.
...
HTTP Error 403 - Forbidden

permissions would not be my first guess for the cause of the service unavailable error. What is the error number on that?

[Sargera]

The error number is 503, and I know it is a permissions error due to the messages in the Event Viewer. Application pool conflicts are the source of the problem (you can tell because if you start the application pool up and visit the website, the app pool stops and a message in the event viewer pops up).  For more info on 503 errors: http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html

[Sargera]

Hmm...Help?  

[muert0]

http://support.microsoft.com/?kbid=823159

[Sargera]

Already looked there, and it doesn't apply to Windows Server 2003, Standard Edition (see first post notes).