Black-flash (single frame of black) towards start of render-result when rendering a whole project (12min 30sec), but this doesn't occur when rendering just the initial section (to 1min 3sec) including the "flash" point)..
Workaround: combine the two renders in a separate project, use the short one to patch over the black-flash in the long one. Like I've had to do in the past...
Project and footage are both 720p50 "MXF for NLEs" obtained from a Sony PMW-EX3 via Sony ClipBrowser 2.6. I know Vegas 9 can import EX3 files directly but find MXF easier to work with. Just reporting here what seems like a bug (though who knows where!) and to find out if it is a known issue etc.