My Xbox has been running fine for about 6 years. The other day (when some in-laws were messing with it) it suddenly loads and runs Evolution-X EXTREMELY slow. Instead of the usual fluid motion, it goes 'chop', 'chop', 'chop', about one every second (you can actually hear the HD chop together with the motion.) It is still possible to use (even though it takes a few minutes to load and another few minutes to choose a program to load.) HOWEVER, once you load a different program, for instance XBMC, then everything runs fine.
I've tried booting from my Evolution-X boot CD, but the problem still remains after a successful CD boot. (strange, I know)
I've been thinking about installing another dashboard, but I'm not sure if that will help. Plus, I really liked the setup I had in Evo-X.
I don't exactly understand how, but I've fixed the problem. All I did was start a game (SSX Tricky) from the loader program I have, and after I exited the game to go back to the dashboard (by holding both triggers and start and select), it miraculously was working again! Now it turns on and runs the way it should. :o)