Error: Failed to upgrade SharePoint Products and Technologies

The scenario:

When I try to add a new Web server to an existing farm with no Web applications, after installing the server I ran the SharePoint Products and Technologies Configuration Wizard & receive the following error message:

An exception of type-Microsoft.SharePoint.PostSetupConfiguration.PostSetupConfigurationTaskException was thrown. Additional exception information: Failed to upgrade SharePoint Products and Technologies.

And additionally, the Upgrade.log file contains the following error message:

The access control list on %system root%\Program Files\ Common Files \Microsoft Shared\Web server extensions\12\template\layouts\Web.config could not be modified because the path could not be located in the file system.

Why it happened?

This error occurs when the SharePoint Products and Technologies Configuration Wizard cannot locate or modify the Web.config file.
The reason for this error was because the SharePoint Products and Technologies Configuration Wizard cannot locate or modify the Web.config file - which was supposed to be in the 12\template\Layouts folder

How can I fix it?

1. simply copy the Web.config file from the following folder:
%system root%\Program Files\ Common Files\Microsoft Shared\Web server extensions\12\Config

2. plant it in the following folder:
%%system root%\Program Files\ Common Files\Microsoft Shared\Web server extensions\12\Template\Layouts.

3. Run the SharePoint Products and Technologies Configuration Wizard again

Microsoft Technet link

Error: The database is not consistent with the expected database schema version

After upgrade from standard license to an enterprise version of SharePoint 2007, one of my customers Starts to notice a repeated error in the event log under the application section.

Event Type: Error
Event Source: Windows SharePoint Services 3
Event Category: Topology
Event ID: 5617

The error massage was:

The schema version (3.0.149.0) of the database SharePoint_AdminContent_xxxxxxxxxxxxxxxxxx on x64a is not consistent with the expected database schema version (3.0.150.0) on XXX. Connections to this database from this server have been blocked to avoid data loss. Upgrade the web front end or the content database to ensure that these versions match

The Solution was very simple:

stsadm -o upgrade -inplace -url http://{relevant central_admin_url}

In my case that seemed to have solved the problem.