Session object available only in one page

[eluser]Alhazred[/eluser]
Yes, that's empty.
It looks sure that my session is regenerated at each page load, but I don't get why.

[eluser]Alhazred[/eluser]
I've finally solved using the code suggested here
http://ellislab.com/forums/viewthread/161213/#774920

and setting the session's expiration time to 0, because of the timezone, using 7200 the session resulted expired as soon as created.