Thanks, [NAME] !  Dell Command | Update 4.0 can be downloaded from [URL]
DCU has worked very well on this system for several years, and the current version (3.1.2) has worked well for some months.  Suddenly it has started hanging with the mesages I have tried disabling the antivirus software, running DCU with admin privilegies and running the system in safe mode (then DCU did not start at all).  I have also tried reinstalling and donwgrading to previous 3.x versions.  Nothing helps.  Any suggestions on how to fix this?
Dell Command Update 3.1.2 hangs with "Operation in progress".