I have just been playing around with the graphic -
I have cut the graphic down to simply a series of three differently colour squares in a row with (roughly) a 5mm gap between them. No animation. Just one layer with the squares.
When I export to SWF from Illustrator, then import the SWF in Quark, i still get the solid black preview.
However, if I move the coloured boxes so that they overlap, I get a proper preview in Quark.
If I then move the right hand box further away so that is not touching, and export etc. I get the proper preview.
Then, if I move the the second box away from the first, I get the solid black preview!!
Why???