Index: trunk/psModules/src/imcombine/pmSubtractionParams.c
===================================================================
--- trunk/psModules/src/imcombine/pmSubtractionParams.c	(revision 14733)
+++ trunk/psModules/src/imcombine/pmSubtractionParams.c	(revision 14734)
@@ -251,4 +251,11 @@
                 sum1 += 1.0 / *wt;
             }
+        }
+        if (!isfinite(sum1)) {
+            psError(PS_ERR_BAD_PARAMETER_VALUE, true,
+                    "Sum of 1/sigma^2 is non-finite for stamp %d (%d,%d)\n",
+                    i, (int)stamp->x, (int)stamp->y);
+            psFree(kernels);
+            return NULL;
         }
     }