I have a Pi 2 B with official 7" touchscreen that is failing during the boot sequence. I'm running fully up-to-date Jessie, and the Pi boots with no problems with HDMI. When I connect the touchscreen, the Pi boots and the display works fine for a few seconds. It makes it as far as recognizing USB, then the screen gets snowy and fades to white and the Pi reboots.
I've checked all the connections and everything seems fine, and it seems unlikely to be a connection problem since the display is working for a few seconds. Help is appreciated. Thanks!