Instance of class DateTime returns empty object

Hello,

we have a problem with the PHP-class DateTime one a Debian-
Server. After we creating a new instance of the class, we get 
just an empty object:

$date = new DateTime();
var_dump($date); // object(DateTime)#2 (0) { }

The common methods for the class are available.

On a local machine, DateTime works fine without issues.

Server-specs:
- Debian 5.0.7
- Apache/2.2.9
- PHP Version 5.2.6-1+lenny9

Somebody an idea? Could this be a problem with a config?


Thank you, greetings,
David