Continual reboot

This looks like a great app but having a few probs. I have ATV 2.1 although aTV flash install guide says do most recent update, i resisted going 2.2 due other issues i have read and stuff here. Maybe this is my first obvious error. However, all installed seemingly ok, ATV rebooted and i’ve reached the ATV menu plus extras. The problem is that it seems to reboot after a short time - apple logo then quick blank screen apple logo again then eventually normal menu once more. I can then navigate as normal until the reboot happens again after a short time.

Please help, otherwise this seems to be what i’ve been looking for.