Phone goes to sleep

Hi again, just downloaded new version 3.2, and yes the “leave backlight on” has been changed to “prevent auto-lock” however that is checked by default and I still have the same problem, that is that the phone goes to sleep after about 2 minutes.
Again any suggestions? The 2 min time out is the one I have set for my screen time-out after inactivity and is set through the OS.
Thanks again
Tony