2. Quicktime 7.2 installed (this also happened with v7.1.5 installed)
3. It *seems* only the clips that play BLACK are those that have more than ONE video effect applied to it. Like, Levels and ProAmp, or Color Balance and Levels, etc. Levels alone, or ProcAmp alone will let the clips render and play just fine.
4. *But*, at least ONE clip on my timeline has 2 effects on it (Levels and Color Balance), and it PLAYS. Go figure.
Wait, this just in, they guy who's editor that is just told me that some clips still won't render regardless of the number of effects applied to it (i.e., none, one, two, etc.).
And even at least one clip with NO effect simply won't play; it's just black, but the associated audio with it does play.
So, all my theories are blown out of the water.
Here's something else to ponder: two of our four AJA Xena workstations mysteriously had their keyboard shortcuts reset to the defaults. It appears to have happened overnight. Was there an Adobe update that is causing all this woe?