Can't figure out how to fix codeigniter's sessions not saved

I'm using php 5.4.17RC1 moved from a server with php 5.3, since then codeigniter's session aren't working (or working sometimes..)

I saw that there's a difference between the phpinfo on my old & new server which is: Registered save handlers = files user (new server) Registered save handlers = files user sqlite

Does anyone have a clue??

Thank you