PROBLEM: Pressing the power button on Xbox powers the unit up and can be seen on TV, but there is no lights illuminated on the console front and the xbox controllers will not connect. A universal remote can and does work to control the Xbox.
SOLUTION: I fixed this by simply unplugging the power adapter from the back of the Xbox for 5-10 seconds (NOT THE WALL, the power brick is a huge capacitor and would take a significant amount of time to drain power completely, to reset the Xbox.
I saw many post around the web with others that seemed to have experienced this issue. Hope this helps.