Problem by Module mISDN

Hello i have a Debian Etch 4.0 Server with Apache2, PHP5, MySQL, Asterisk 1.4-current, mISDN 1.1.8 and FreePBX 2.5.1-current.

I would like mISDN Module after this guide

if I want to activate the module the following error:

Fatal error: Call to a member function load() on a non-object in /var/www/asterisk/admin/modules/misdn/ on line 38

Please can help me !!!