My box (xr4500) also kept rebooting. Screen image would flicker on and off every 2 seconds. I could see message on screen saying buzztv5 keeps turning off with options to 1) show info and 2) turn off application (not sure of exact wording. going by memory). When image flickered on, I pressed ok on my remote to choose "show info". And I was able to see a stable screen. I scrolled down and cleared cache. I think I also chose force stop (not sure). Went back to home screen and it was still flickering and rebooting . I chose "live tv" and it was stable. So, I left it for 30 minutes as I read somewhere that the application would update again minutes after initial update to Buzz5. After 30 minutes I checked for update and It installed the latest stable IPTV version. Could be just luck, but that's what happened when I updated my box to Buzz5.
Recap:
1) make your way somehow to buzztv settings and clear cache
2) wait 20-30 minutes after install of buzz5
3) check for updates