When I work in a 2D drawing apparantly some of my lines are slightly off in the z axis and I can't fillet.  I get the 'cannot fillet co-planar lines' type warning. I know how to move those lines to be parallel with the rest, but is there a way to fix this problem globally?  I am learning how to work in ACAD 3D so I can fix the problem line by line... but I suspect there is a simple command to set all lines to 0 on the z axis or something similar.   These are usually drawings that have been started by someone else...  I don't think it has ever happened when I start with a new file... which is rare in the company I work for, you know...
 
Any help would be appreciated!  thanks! 

Use the "flatten" command to globally move objects to "0" elevation.