Philippe,
Sorry for the time delay but here is a follow up on the post I made on the Trixbox.org forum http://trixbox.org/forums/trixbox-forums/open-discussion/does-anyone-have-directed-call-pickup-working#comment-139517. I have tested this on a CentOS 5.2 system with Asterisk 1.4.22 and FreePBX 2.5 and it has the same issue as FreePBX 2.4. If you have Follow-Me settings configured for an extension and have disabled it with the checkbox on the extension configuration page then directed call pickup will not work. I have tested with internal calls and external calls, the configuration is basic extensions mode, no ring groups or pickup groups. I have attached the pertinent portion of the log.