I have seen many questions regarding rebooting issues when shuting down the Pi.
I have a Pi with Raspbmc installed and just happen to have the opposite problem: any reboot command (whether through XBMC menu "Reboot" or SSH "sudo reboot") will cause my Pi to shuts down without rebooting - I then have to hard reboot through power unplug/replug. Not so great for SSH remote management.
Incidentally, I use a powered-USB hub to both connect more peripherals and power my Pi.
Has anyone had the same problem? Any idea how to fix the issue?