I'm trying to track down a device in my house that also makes a beep-beep noise at irregular intervals... I've slowly narrowed it down to the N800 through a process of elimination - it most recently went off 14 minutes ago, but I probably won't hear it again for several hours if not days (assuming it goes off when I'm asleep/not around to hear it). I've no idea what causes it - the "beep" is quite tuneful, more of a polyphonic "duh-duh" in my case. I've no alarms set either. Isn't a low-battery warning as the device is currently charging, I put on charge about 20 minutes before it's latest outburst and it was on 4 bars to begin with (still charging, not yet reached full charge as I type). Quite possibly only started since the 3.2007.10-7 update, but I couldn't swear to it. Most odd.