diff -r 98b1778f0fd1 -r 8172fc66e135 jdk/src/windows/native/java/net/TwoStacksPlainDatagramSocketImpl.c
--- a/jdk/src/windows/native/java/net/TwoStacksPlainDatagramSocketImpl.c	Tue Apr 06 13:47:59 2010 +0100
+++ b/jdk/src/windows/native/java/net/TwoStacksPlainDatagramSocketImpl.c	Tue Apr 06 15:44:17 2010 +0100
@@ -1579,7 +1579,7 @@
     jobject addr;
     int i;
 
-    if (ni_addrsID == NULL) {
+    if (ni_addrsID == NULL || ia_familyID == NULL) {
         jclass c = (*env)->FindClass(env, "java/net/NetworkInterface");
         CHECK_NULL_RETURN (c, -1);
         ni_addrsID = (*env)->GetFieldID(env, c, "addrs",