Invalid library (maybe not a PHP library) error

Hello, On Loading my PDO-interface based driver, PHP gives the error: "PHP: Startup: Invalid library (maybe not a PHP library) 'php_pdo_xyz.dll in unknow on line 0 " I wrote a PDO-based driver, modelling the code on lines of SQLite driver. Compiled my driver as Dll , added the extension to php.ini. on running PHP, I get the above err . To add: I used DependencyWalker tool to see if I have missed some Dll, I find that tools seems to find my Dll fine. The output list of Dll pdependancies of my driver-Dll looks exactly like that of php_pdo_sqlite.dll Please let me know, where could be the potential problem. thanks, -sanjeev kumar