I recently came across this previous locked thread http://www.geekzone.co.nz/forums.asp?forumid=82&topicid=105672 about several people with the Genius that would reboot every 28 hours.
I have the "GeniusLite1400" firmware and I get this issue too. In the other thread it was said that the newer firmware can fix the issue BUT that firmware has issues with fibre (that haven't been fixed a year later????).
Just wondering if there's a workaround floating about besides buying a new router 'cause this is beyond mere annoyance for me, I work from home and it can sometimes cost me a lot to lose connection for a couple of minutes.