When trying to create a 3D object using any of the surface modeling tools with spline/bezier paths of any type, the paths disappear upon applying any of the surface modeling tools and no 3D shape results. Basically applying the surface modeling tools to line paths simply deletes the paths but yields no 3D object. Has anyone else experienced this and or have any solutions? Thanks.

Same here, but I assumed I wasn't understanding yet how the tool worked.

I suspect that the paths aren't actually touching each other. They MUST connect or you can get disappearing content. When drawing to or from an existing path, hold the Shift key. It will show a little, white cross-hair that will snap to the line and/or beginning and end points as you move the cursor over an exiting line. Put it where you want it and then click to begin drawing.

What about the case of ruled line objects where the curves can't (or not really feasibly) touch?

You're correct for ruled surfaces, nothing is touching. Does your geometry still disappear? I just completed a project with ruled surfaces and didn't have any issues. If it does, we'll have to poke around a little more and see what's up.

It occurred to me there maybe some stray "temp" files floating around and causing problems. I did a find file for "temp" and threw away the the ones associated with Eovia. That seemed to solve the problem. Thanks for your responses.