i very much doubt its nVidia that is causing the problem...
the DBProAssist is the program which checks to make sure you have legal version of the software.
if it isn't working try uninstalling and reinstalling as no doubt the file has been corrupted along the way.
also make sure your using the DBpro CD in the drive you installed it from, and don't use a copy of the CD only use the official CD because when you copy the CD even if you use specific copying software you won't copy the protection part of it.
if all this fails, email Lee