600D / T3i / Kiss something something

I can't get the raw video to create files.
I have 2.3 plus the nightly build (5-29-13) plus the Tragic Lantern build (800 Fileman)
I keep getting "File Create Error" and record doesn't run. I can shoot regular ML video no problem.
I have a fast card (Sandisk Extreme Pro 10).
I've turned off all enhancements and ML options except raw video and set the size to the minimum.
I've also changed RAW to sRAW in the shoot menu.
But just can't get it to shoot video :-(
Have I missed something obvious?