Application Web Config for this IIS site (601773052) could not be found at C:\Inetpub\wwwroot\wss\VirtualDirectories\XXX\web.config.

After running a sharepoint patch the configuration wizard would fail on one of the farm servers towards the end w/o any identifying information. These are some of the error messages that I received in the upgrade log(located: program files/common files/microsoft shared/web services../bin/logs):

Application Web Config for this IIS site (601773052) could not be found at C:\Inetpub\wwwroot\wss\VirtualDirectories\XXX\web.config.

[SPManager] [INFO] [1/24/2009 2:30:48 PM]: Resetting the status of PersistedUpgradableObject: SPWebApplication Name=WEBAPPLICATIONNAMEHERE Parent=SPWebService to Online.

[SPManager] [ERROR] [1/24/2009 2:30:48 PM]: ReflexiveUpgrade [SPWebApplication Name=WEBAPPLICATIONNAMEHERE Parent=SPWebService] failed.

Well thanks to MS KB944267

I was lead to look for the web.config file which did not exist on the problem farm server. I copied the files from the WFE- inetpub/wwwroot/virtualdirectories/WEBAPPLocation to the same directory on the farm server missing the files and that fixed the problem

How to troubleshoot common errors that occur when you run the SharePoint Products and Technologies Configuration Wizard on a computer that is running

This article describes how to troubleshoot some common errors that occur when you run the SharePoint Products and Technologies Configuration Wizard after you upgrade a computer that is running Microsoft Windows SharePoint Services 3.0 or Microsoft Office SharePoint Server 2007.

http://support.microsoft.com/kb/944267

MOSS Version Numbers

How to check SharePoint Version level running:

1) Goto IIS, select the MOSS website
2) Right click and select Properties
3) Select HTTP Headers tab and you should be able to see a custom HTTP Header called "MicrosoftSharePointTeamServices" with a version number by its side.

MOSS 2007 or WSS 3.0 Hotfix (KB953484 - KB953473 - KB953471) 12.0.0.6317.500
MOSS 2007 or WSS 3.0 Hotfix (KB953138 - KB953137) 12.0.0.6316.500
MOSS 2007 or WSS 3.0 Hotfix (KB952704) 12.0.0.6315.500
MOSS 2007 or WSS 3.0 post-SP1 hotfix (KB952294) 12.0.0.6314.500 [In SSP admin you will get a new Search Administration option, which brings the Search Server features to MOSS.]MOSS 2007 or WSS 3.0 post-SP1 hotfix (KB948945) 12.0.0.6303
MOSS 2007 or WSS 3.0 post-SP1 hotfix (KB941274) 12.0.0.6301
MOSS 2007 or WSS 3.0 post-SP1 hotfix (KB941422) 12.0.0.6300
MOSS 2007 or WSS 3.0 SP1 12.0.0.6219
MOSS 2007 or WSS 3.0 October public update 12.0.0.6039
MOSS 2007 or WSS 3.0 August 24, 2007 hotfix package 12.0.0.6036
MOSS 2007 or WSS 3.0 RTM 12.0.0.4518
MOSS 2007 or WSS 3.0 Beta 2 TR: 12.0.0.4407
MOSS 2007 or WSS 3.0 Beta 2: 12.0.0.4017

Credit: Boby Habib