How are you setting the timeout? There are two different settings which affect this - System→Preferences→Screensaver sets the time until the screensaver kicks in (which is possibly just “blank screen”) and whether it locks your session, and System→Preferences→Power Management sets the time until your screen is turned off.
Are both set to the values you desire, and still being ignored? Or have you just missed one of these places?
How are you setting the timeout? There are two different settings which affect this - System→ Preferences→ Screensaver sets the time until the screensaver kicks in (which is possibly just “blank screen”) and whether it locks your session, and System→ Preferences→ Power Management sets the time until your screen is turned off.
Are both set to the values you desire, and still being ignored? Or have you just missed one of these places?