Bricscad 12.1.2
OpenDCL  7.0.0.1
Win XP

A small problem with DwgPreview:
To load a new dwg in a preview you have to first make it invisible.
See attached files.

Put all files in a single folder.
Open one of the drawings.
Load the lisp.
Enter BKG_BLOCKBROWSER to run.
Hit Reload button.
Result: only BkgBlockBrowser_Main_DwgPreview1 has been updated.