[LAU] Jack0.116.2+svn3592-2 disconnect Ardour very often

Hi list, Met a problem, with Jack as far as I can understand... I installed Jack + lib and dev + qjackctl from the Sid repositories on this Lenny based P4 machine with Fluxbox as WM. Then build Ardour from svn. When do any change in an Ardour session, at the next PLAY it says Jack disconnect Ardour cause it was not fast enough, and ask to try to restart Jack, reconnect Ardour and save the session. Nothing can be done, and Ardour is freezed. When restarted, all connections have disappeared... I try with a version of Ardour from the repos, and it's the same, so think problem is on Jack side. Is someone in the list have had the same problem, and/or an idea to solve this ? Any help will be appreciate, thanks ! Freely --fred