Sam,
Using all native Vegas Pro tools there are three elements here.
The text which is expanding. Can be done with track motion.
The flash-line which is a white solid with a mask that quickly reduces it to a line that has a gausian blur on it.
The text and line do a long fade
And the black background, which is a solid.
It looks much cooler with the sound effects.
I put a .veg file here.
4731_flashtext.veg.zip
Jeff
2-Xeon X5680 @ 3.33, EVGA SR-2 Mobo, 48GB DDR3, GTX 580 3072MB, 16TB Attached Storage, Win7, Vegas 11 x64