Wrap this in a try..catch block so you can output the message of the exception and get more information on what's going wrong. I think the com object isn't registered on the server but have a look at the exception for more info.
try {
$obj = new COM("SimplAt1Com.SimpleObj") or die ( "Unable to instantiate the COM!");
$result = $obj->put_Name("A") ;
} catch (Exception $e) {
echo 'Caught exception: ', $e->getMessage(), "\n";
}
Good luck!