The 1st time I tried to record it lasted just about a minute and then the camera reported 1 skipped frame and locked up, so I had to remove the battery. After that it recorded for 5 minutes straight with no issues whatsoever.
I have same problem on my 50D. Right now Im on nightly from 22.3. and it was same on older build from beginning of March. I will try it again on latest nightly build soon and report back.
I get those "1 skipped frame lock-ups" very often. About 1/4 of all cases and it is very annoying as you must turn it of, remove battery, turn on (then it skips modules) so you have to turn off again and then on. Now I have next try

) Sometimes problem repeats couple of times. This drives not only me, but even my unpatient wife very CRAZY :-)
Scenario is always the same. I start recording. 50D starts record session and displays indicator on screen. Now it either continues smoothly without any problem, OR it indicates 1 skipped frame and immediately crashes. Now you are not able to stop recording or do anything else... RAW file is not saved. This happens in both full sensor mode and in crop mode.
Im set like this:
This is
RAW Rec on
1568x882
Global Draw on all modes
Zebras on
Spotmeter off
Waveform off
FPS Override on 23.976 (tried both Exact FPS and optimize for Low Light)
Expo. Sim on
File Manager on
RAW Play on
Using Komputerbay 64 GB 1000x card
So now we know that problem is in both MLV and in RAW recorder. What I want to try (if this will still happen on latest build) is to set frame skipping to be allowed. Now I have it set to stop on skip.
Let me know if you need any further info or something to try... I will update in next few days.