custom session problem with 4.1.2

Hi I have recently had to move some of my php software over to run on a Debian (stable) box with php 4.1.2 and am having some problems getting custom sessions (mysql) to work properly when register globals is set to off. The session will not get written if reg globals is off and the session id is brand new. If I turn on reg globals for the first request, the session data gets written fine to the database; I can then turn reg globals back off and the sessions will read and write fine. It seems like a bug but I may be missing something obvious as I don't have much experience of php before 4.2 any pointers appreciated. regards cyril