This is an updated patch for the one with the Bug item: "[ 1611725 ] Authentication should be abstracted" (http://sourceforge.net/tracker/index.php?func=detail&aid=1611725&group_id=139987&atid=745139)
I cannot attach it there, because I have not been logged in while POSTing.
The only change is that $this->session_init() gets called in the session data handling methods. The original patch would not work at all.
Sorry.
Updated patch against 2.0.0