I have a network drive letter L mapped to a drive folder:

which DraftSight V1R3.1 x64 fails to see:

though DS does see network drive letter O: mapped to a drive root and all other programs here inc. AutoCAD and Rhino 3D see all drives fine e.g:

This on Win7 Pro 64-bit, with network drives on Win XP SP3.

Any ideas?