The application written in ASP with dll and etc and use ODBC for database connection. Everything working fine but one day there was a auto windows update can cause this ASP application running with error message "data source name not found". Plenty of time taken for debugging and not solved. Finally by trial and error, the problem solved. Strange, the problem is caused by the permission setting on the dll which call the ODBC. We suspect the problem cause by the windows update and change the permission setting.
Hope this help.