This error is not logged to the event log as this is a SharePoint error triggered before our software is started. To get more detail about the error, temporarily change the 'CallStack' attribute in the 'SafeMode' element in the web.config to 'True' and change the following mode to "Off": <customErrorsmode="Off"/>.
Default path to web.config file is:
c:\inetpub\wwwroot\wss\VirtualDirectories\80\web.config