Assembly drawing XREF paths

Most of the things I design are very simple.  Because of this, I only rarely make assembly drawings.  On the occasions I have, I usually copy and paste the parts from other drawings, and fit them together with ESNAPS.  If I want to rotate or move the assembly, I group them with the BLOCK command. 

Last week however, I needed an assembly drawing of a more complex design.   I decided to use the assembly tools in BricsCAD.   I placed the *.dwg's for all the parts I wanted , in a subfolder "\Parts".   I then used BMINSERT to build my assembly.   This caused XREFS to be generated.  I never liked XREFS, because the absolute paths get broken if you move the project folder to another computer or network drive.  

In fact, this is what I encountered when I moved my new project folder.   So I opened up the drawing explorer and changed the paths for the XREFS from an absolute to a relative reference..  For instance:

c:\users\jimc\desktop\project\Parts\hinge.dwg

became

.\parts\hinge.dwg


Now  I could move my project folder anywhere I liked, and the assembly was still viewable.
However, I noticed a problem.  While the paths were still absolute, I could edit any of the parts, and the change would be reflected in the assembly as soon as I ran the command BMUPDATE.  However, after I entered the relative path, BMUPDATE no longer did anything.

Can someone tell me what I am doing wrong and how to fix it?