Union Errors in AutoCAD

[indieFan]

Please read the following carefully before you make any comments. Thanks.

I have been trying to create a truss system for a model using AutoCAD. I had finally gotten the entire thing done only to realize that the diameter of the pieces were incorrect. I have since restarted the truss with the correct diameter. There are three errors that I have come up with in this process:

1. Inconsistent face-body relationship
2. Inconsistent edge-face relationship
3. AG curve *something*

I have tried adding a sphere to the end of the cylinder to attach it to a corner, but this failed. I checked to make sure that the corner was completely solid, which it is. I then decided to check whether both parts were valid solids. The cylinder is, however the large piece that I'm trying to attach it to is not.

The questions I have are:

1. Have you come across these errors? (Especially the third.)
2. How do you suggest I remedy the issues?
3. Would be it better to build a truss out of square rods instead of round?

Thanks,
indieFan

P.S.-I've tried to attach the latest copy of the file, but I can't save it as anything but a bitmap which is too large. I'll try again from home.