I have installed DB2/iSeries .net driver on my 32bit(Windows 2003 R2) and 64bit(Windows 2008) production servers, which are having .net ver 3.5 SP1 and ver 4.0 respectively.
This is caused to stopped running ASP.net applications.
You will received above error or “Service Unavailable” error message.
The reason is, as screen shot showing read/read-execution permission of IIS service account to read machine.config has gone.
Set permission for IIS_WPG user as follows,