Sndfile-info from terminal showed me that the problem was in the name of the folder that contains my session! there was a ":" and a "&" in the name of the folder that ardour, and maybe not only ardour, disliked.

When i changed the name, the session started regoularly with all the regions.

2011/6/16 Paul Davis <paul@linuxaudiosystems.com>

On Thu, Jun 16, 2011 at 3:11 PM, Paul Davis <paul@linuxaudiosystems.com> wrote:
>> ps. i don't know if it is exactly the right place to post this question, i
>> even wrote it on ardour forum..
>
> this is the right place; the forum is, IMO, the wrong place.

i go tthat wrong. ardour-users is the right place, but this one will do :)