Index: gui/wxpython/vdigit/driver_draw.cpp
===================================================================
--- gui/wxpython/vdigit/driver_draw.cpp	(revision 41236)
+++ gui/wxpython/vdigit/driver_draw.cpp	(working copy)
@@ -150,6 +150,7 @@
 			isles[j] = NULL;
 		    }
 		    G_free((void *) isles);
+		    isles = NULL;
 		}
 	    }
 	}
Index: gui/wxpython/vdigit/line.cpp
===================================================================
--- gui/wxpython/vdigit/line.cpp	(revision 41236)
+++ gui/wxpython/vdigit/line.cpp	(working copy)
@@ -798,6 +798,7 @@
     if (bgMap) {
 	Vect_close(bgMap);
 	G_free ((void *) bgMap);
+	bgMap = NULL;
     }
 
     return ret;
Index: gui/wxpython/nviz/init.cpp
===================================================================
--- gui/wxpython/nviz/init.cpp	(revision 41236)
+++ gui/wxpython/nviz/init.cpp	(working copy)
@@ -187,6 +187,7 @@
 
 	PyFile_WriteString(sentence, pyFd);
 	G_free((void *)sentence);
+	sentence = NULL;
 
 	PyFile_WriteString("\n", pyFd);
 	start = next;
Index: gui/wxpython/nviz/surface.cpp
===================================================================
--- gui/wxpython/nviz/surface.cpp	(revision 41236)
+++ gui/wxpython/nviz/surface.cpp	(working copy)
@@ -346,6 +346,7 @@
 	}
 
 	G_free(surf_list);
+	surf_list = NULL;
     }
 
     return 1;