This error was coming up in Sharepoint’s Central Administration page, so first locate  the config file for this site:

1. Right-click My computer, select Manage. Then go to Services and Applications, and select Internet Information Service.
2. Open the Web Sites group, and find the web site giving this error. Right click, choose Properties, go to Home Directory tab. The local path then shows you where the config files are located.
3. Go to that directory, and open web.config, edit as follows (take a backup first!):
   • Change as follows: find  SafeMode MaxControls=”200″ CallStack=”false” , change it to SafeMode MaxControls=”200″ CallStack=”true“
   • Also change CustomErrors mode=”On” to “Off“

OK! So now I could see my actual error message, which went something like this:

The SiteMapProvider ‘SPXmlAdminContentMapProvider’ cannot be found.

So back to web.config – a search for SPXMLAdmin found nothing…. so I located an old copy of this file, and copied this in just before the </providers> </sitemap> tags:

<add name=”SPXmlAdminContentMapProvider” siteMapFile=”_app_bin/admin.sitemap” type=”Microsoft.SharePoint.Navigation.SPXmlContentMapProvider, Microsoft.SharePoint, Version=12.0.0.0, Culture=neutral, PublicKeyToken=71e9bce11e9429c” />

And voila! Central Administration back up and running. Note that I assume that my Public Key Token is unique to my install, and you would need to use the PublicKeyToken from your other web.config entries.