Index: /trunk/Ohana/src/getstar/src/args.c
===================================================================
--- /trunk/Ohana/src/getstar/src/args.c	(revision 20984)
+++ /trunk/Ohana/src/getstar/src/args.c	(revision 20985)
@@ -122,4 +122,13 @@
 	SWAP (REGION.Dmax, REGION.Dmin);
     }
+
+    R = REGION.Rmax - REGION.Rmin;
+    D = REGION.Dmax - REGION.Dmin;
+
+    if ((R <= 0.0) || (D <= 0.0)) {
+      fprintf (stderr, "WARNING: selected region [(%f,%f) to (%f,%f)] has zero or negative area\n", 
+	       REGION.Rmin, REGION.Dmin, REGION.Rmax, REGION.Dmax);
+    }
+
   }
   if ((N = get_argument (argc, argv, "-radius"))) {