Ooops. Power failure exactly after writing the restart .vel and .xsc and opening (but not writing) the .coor. The result was an empty restart.coor. Because (through the NAMDautorestart script) I foolishingly deleted the restart*.old files, no restart files were available. Because I also foolishingly deleted the RUN_??.dcd file, no restart file could be prepared. Nice job, well done …