Screen timeout stopped working.

[subeh.sharma]

I've Galaxy S with Android 2.2. Recently i've noticed that screen backlight won't go off after the set time of 15/30 seconds. When i go under settings, i see no option has been set i.e. no radio button(each corresponding to a time interval like 15 sec, 30 sec) is selected. I then manually select that and phone starts working okay for few days but again shows this problem.

Any idea?