Eric:
Yes, I am using 3d simple line symbol with style set to tube. Not sure what's happening here, but now I am getting the elliptical result with my personal geodatabase line feature class as well. Could it be a setting I have, video card, etc?
My co-worker submitted a sample dataset for repro this morning to ESRI Technical Support. I guess I was hoping to see if this issue was/is happening to others as well in hopes of a quick resolution.
Regards.