session_id

hi,
i have installed rcmail and think thath it's very good module.
But i have problem with single sign-on. When i click on roundecubemail menu, into iframe roundecube in form me of failed login and form it 's empty. If i insert credential it works.
I have tried to view what your patch it do and problem it seems being session_id. it return a value wrong that ago to fail query: it return null value.
You can help me?