can't check tracks boxes for export

Hello , I have been using ardour for a while on OSX with JACK and the MOTU 828 or the internal Mac audio hardware, but now (ardour 2.3) there are several sessions that don’t allow me to check the master:out1 and master:out2 boxes when trying to export either a session or a selection.
I have tried (I think) all the possible settings for the master track Output routing in the mixer window… with no change.
Some sessions, though, still allow me to export normally…

This is a known problem on the Mac version. We don’t yet understand why, and if we did, we’d have solved it already. Probably a good idea to file this in the bug tracker so we don’t forget it. There is a vague chance that its been fixed in the most recent OS X versions.


Seems like I can bring some more information about my problem :
I discovered that any session previously created with ardour 2.0 could allow to export sounds, while more recent ones did not.
To sum up, when using Ardour 2.3 on MacBoook Intel under os 10.5.2, I can not create a session that will allow to export sound (reason : disabled check boxes for choice of tracks to export), but I can open a session created with Ardour2.0 and export.
And when using Ardour 2.0 , I can open a session created with Ardour 2.3 and export !