The story:
User has a drawing with a handful of xrefs, the topmost of which is electrical and has some leaders with arrows showing runs. There are 2 clipping planes, dividing the drawing into 3 - low, medium and high elevations. (shown in plan).
There are some leaders (these are just old-fashioned leaders, not multileaders) that are showing up on the drawing, but not on the xrefs. They DON'T EXIST...
User did everything to clean up all xrefs, re-did the planes, did a wblock/entire drawing, detached/reattached the (apparent) offending xref...everything. Checked the layers...you know..the works.
Finally, she decided to remake the drawing entirely, noticing, as she did, that the template to which her new drawing was defaulting was the Acad.dwt vs Acad3d.dwt, so she started her new drawing using Acad3d.dwt and...Poof!Bang!Voila!...all was again right with the world.
Now, personally, I don't understand how in the world this would make a difference (neither template has been modified), since, it seems to me that the Acad.dwt in its virgin form would be the most innocuous thing in the world, certainly not the cause of such bizarre consequences.
Has anyone else seen such a thing? While I will bear in mind this possible "fix" for my users who are having weird 5h*t-o-meter stuff going on with their drawings, I would really like to know WHY this would cause a problem.