Index: trunk/psModules/src/objects/pmSourceFitModel.c
===================================================================
--- trunk/psModules/src/objects/pmSourceFitModel.c	(revision 25754)
+++ trunk/psModules/src/objects/pmSourceFitModel.c	(revision 26070)
@@ -91,4 +91,10 @@
             if (!isfinite(source->pixels->data.F32[i][j])) {
                 continue;
+            }
+
+            // skip nan values in image
+            if (!isfinite(source->variance->data.F32[i][j])) {
+	      fprintf (stderr, "impossible! %x vs %x\n", source->maskObj->data.PS_TYPE_IMAGE_MASK_DATA[i][j], maskVal);
+	      continue;
             }