Thanks for the help guys. Still not there though.

Here's another STL that doesn't work and is a wheel. I borrowed this from a Karmann Ghia model on 3Dwarehouse for sketchup. Same problem different wheel.
Wheel_only.stl

Sketchup is awfully particular whenever I make or edit solids, so I'm finding it hard to believe that there's something wrong with the model I made, and it just so happens to be the same, exact, identical problem with some other wheel (the wheel from the Karmann Ghia). Just doesn't make sense that it's the models.

For the folks that ran the model through netfabb, here's the sliced screen captures I see...
repaired1.jpg only 5 lug holes now
repaired2.jpg filling in the area above the wheel lug flange
repaired3.jpglooking like a wheel again
repaired4.jpg oops here's the disc again.

Whether Simplify3d does this properly or not, I've gotten in contact with their tech support. I'm hopeful! I don't currently own their software but would consider it if their product fixes the issue.

Does anyone know if Replicator, Cura, MakerBot and possibly others have a less than ideal slicing engine (or engines)?

Thanks,
Kris W.