I'm seeing a recurring problem when doing renders of complex sequences. By complex I mean eight video layers or more with one or more nested layers, composite modes on at least two layers, and multiple filters on multiple layers.
After the render is complete the video returned from the render file is black.
If I undo and re-render it usually works on the second try.
If I cancel the render when it is partially through and then pick it up, this behavior sometimes start to alternate (first render bad, second render good, etc.) Sadly, this pattern is not consistent.
I've seen this occur with DVCPRO HD, 8-bit SD, and 10-bit SD. I've seen it on software versions 5.04 and 5.12. Also on an earlier version of 5 but I do not recall which.
I've seen this on four different systems over the last 13 months. Sadly, I don't have all the relevant information. The system I saw it on this week is in the shipping cases already.
The lowest end system was a dual G5 2.0 with 2.5 GB of ram running 5.04 with a fw 800 drive as a capture disk and a Kona LH. I saw the same symtoms last month on a Mac Pro 3.0 with 8 GB of ram using an xRaid and a Kona 3. Both systems were rentals, and I did not make note of the QT versions.