@schettj: The only thing i've installed outside of the normal repos is dialcentral, is that known to cause any problems like this?

@x61: If I use root to issue the reboot command it seems to reboot just fine. It's only if I turn it off by either holding the power button down or tapping it and selecting "switch off" that it seems to have the issue. As best as I can tell it never seems to actually power all the way off, as it immediately buzzes and displays the Nokia logo (without turning on the backlight), then buzzes again and repeats the process over and over.