Theres somthing about the first corner, Maybe theres been a spillage of oil on the track or somthing, as Bruno Senna AND another driver both made a Very similar mistake in the GP2 support races yesterday, its either that or there just trying to hard to get a good line out of the corner and missing the apex, thus making then loose all traction and spin the rear wheels.
if you heard what lewis said after the race it was a downshift that locked the rear wheels causing the spin.