Hi,
if you notice that it starts, then starts to read the sd card, then stops, flashes both status lights, then cycle begins aagain THEN it's almost certainly.
a. a failed power supply
or
b. a failing or failed sd card.
If you don't have a spare PS, then try with the SD, format a new one (NON SDHC)
If after the first attempt it stops, it's probably only the SD Card.
A