Did somebody faced same problem: I softmodded my XBOX quite a while ago. It has Unleash loaded first and then I choose XBMC as a program. If I switch off power from XBOX or not use it for several days then it does not load into Unleash and instead loads original XBOX program and at that point I could see that the system time has been reset. I have to enter some DVD into XBOX to make it load Unleash. I thought that was strange but could live with it. Recently I softmodded 2 other XBOXes with single boot option: it loads XBMC straight away. It worked fine and I unplugged both of them from the power. When several days later I tried to turn them on I could not. Both of them does not load XBMC and screen stays black. The only cure is to use softmodding again(insert SPlinter Cell again). Is there a cure against it.
It's because you're disconnecting the xbox from the power, i think it's something like 4 hours that the xbox keeps the time when disconnected. The only way to stop it is to leave the xbox plugged in. You don't need to redo the softmod, it hasn't gone anywhere. Just set the time in the xbox's own date/time screen, reset or restart the xbox and voila you'll find that the softmod was just playing peekaboo....
No problem. I did have one xbox that kept doing this despite being left plugged in (i leave all mine plugged in even if i don't use them for months, just habit). I can't remember how i fixed it in the end as i may well have redone the softmod but i did also redo all the settings, in the xbox's own flubber menu, in UnleashX and in XBMC. But certainly on all the other xboxes it just happens due to being switched off. Just remembered, there's a thread here somewhere that might also help if the issue returns, the xbox has some kind of 'gel capacitor' whereas pc's have a Bios battery. edit, found it ~ http://forums.afterdawn.com/t.cfm/f-58/xbox_goes_straight_to_clock_and_ms_dash-783201/
