Well, the Macbooks' (Pro) power circuitry doesn't seem to be among the best. Alone the fact that the PSU provides *less* power than the Mac may draw (at which times it draws additional power from its battery) does not give much confidence.
There are grounding problems (like creeping current on the aluminium chasis and buzzing sounds from the internal speakers when the PSU is connected).
I had it happen that when I connected a Fireface bus-powered to my 2009 17" MBP the USB port lost it's connection/power for a short moment. As far as I remember RME identified that some Mac don't provide the necessary bus-power that a Firewire port should be able to.
Several time the internal Blutooth device did not activate after a fresh computer sarrt (like if it didn't exist, neither in OS X nor in Windows) and only turning the Mac off/on would make it work.
The FF has a really good range of what voltages you can feed it with, but still make sure you get a really good/stable power-supply. Also try to disconnect everything else (DisplayPort, USB, SD card, even disc from the DVD) and decrease or increase the screen brightness (try both 100% brightness and lowest possible brightness).