As i red to an admin's post, it's seems that i can't set the sleep mode if i don't set the clock first.
Indeed the sleep mode doesn't work so my player's screen stay permanently highlighted while i'm listening music, wich is draining my battery off faster.
When i set the sleep mode (to 10 for example) nothing happens after 10 sec, so i turn off my player (without using the on/off button) and turn on: the sleep mode is reset to 0 again.
The off time mode works perfectly, even when i setup this off time and i turn off my player, it stay at the same delay that i've set.
Any ideas??