Apparently, some people, including me, are experiencing this bug, but the cause of it isn't totally known.
I've noticed that if I try to load X-DSL while my Xbox is connected to an HDTV (in actuality, a 21" computer monitor), the LEDs blink orange, and the Xbox turns off after a few seconds. But, if I load X-DSL while the Xbox is connected to a TV using the standard composite cables, it will load fine.
More information about this can be found in the bugs
forum at ShALLaX.com.