VIEWMOL currently cannot handle GAUSSIAN outputs which contain cartesian f functions (10f).
HPGL or Postscript outputs for drawings which are labelled with non-latin characters will not contain any labels. HPGL output has only support for German umlauts, Postscript provides all ISO-8859-1 characters.
If VIEWMOL has been linked with Mesa and is running on Linux the "Lines while rotating" button should always be set to on (the default). If it is set to off, a model is drawn with surfaces, and tried to rotate, VIEWMOL will crash with a floating point exception. This is a bug in Mesa.