I keep working on my theory that somehow FCP might cause the system shutdown...
here the logs of the last 2 shutdowns, the firstline is spammed maybe 50 times, then the next 4 lines and power goes off...
5/12/14 7:20:58.216 PM WindowServer[84]: CGXSetWindowListAlpha: Operation on a window 0xb8 requiring rights kCGSWindowRightPresenter by caller Final Cut Pro
5/12/14 7:22:36.241 PM Final Cut Pro[525]: AVF error: Perf capability check failed: 0xe00002be
5/12/14 7:22:36.241 PM Final Cut Pro[525]: AVF error: Branch_QT0::pushBits, Context Creation Failed.
5/12/14 7:22:36.328 PM Final Cut Pro[525]: AVF error: Perf capability check failed: 0xe00002be
5/12/14 7:22:36.328 PM Final Cut Pro[525]: AVF error: Branch_QT0::pushBits, Context Creation Failed.
5/12/14 8:19:30.662 PM Final Cut Pro[437]: error: FigTimeGetSampleNumber t.timescale == 0 || Non-Numeric(t) || Invalid(t) || sampleDuration.timescale == 0 || sampleDuration.value == 0 (t=-inf, sd=0.033333(100/3000))
5/12/14 8:19:30.848 PM Final Cut Pro[437]: AVF error: Perf capability check failed: 0xe00002be
5/12/14 8:19:30.848 PM Final Cut Pro[437]: AVF error: Branch_QT0::pushBits, Context Creation Failed.
5/12/14 8:19:31.508 PM Final Cut Pro[437]: AVF error: Perf capability check failed: 0xe00002be
5/12/14 8:19:31.508 PM Final Cut Pro[437]: AVF error: Branch_QT0::pushBits, Context Creation Failed.