http://bzr.savannah.gnu.org/lh/grub/trunk/grub/revision/4548

diff -dur grub-2.00.orig/ChangeLog grub-2.00/ChangeLog
--- grub-2.00.orig/ChangeLog	2012-06-28 02:06:26.000000000 +0200
+++ grub-2.00/ChangeLog	2012-10-28 10:52:48.619830487 +0100
@@ -1,3 +1,9 @@
+2012-07-02  Vladimir Serbinenko  <phcoder@gmail.com>
+
+	* grub-core/net/tftp.c (ack): Fix endianness problem.
+	(tftp_receive): Likewise.
+	Reported by: Michael Davidsaver.
+
 2012-06-27  Vladimir Serbinenko  <phcoder@gmail.com>
 
 	* configure.ac: Bump version to 2.00.
diff -dur grub-2.00.orig/grub-core/net/tftp.c grub-2.00/grub-core/net/tftp.c
--- grub-2.00.orig/grub-core/net/tftp.c	2012-06-22 17:42:07.000000000 +0200
+++ grub-2.00/grub-core/net/tftp.c	2012-10-28 10:52:11.463407895 +0100
@@ -143,7 +143,7 @@
 
   tftph_ack = (struct tftphdr *) nb_ack.data;
   tftph_ack->opcode = grub_cpu_to_be16 (TFTP_ACK);
-  tftph_ack->u.ack.block = block;
+  tftph_ack->u.ack.block = grub_cpu_to_be16 (block);
 
   err = grub_net_send_udp_packet (data->sock, &nb_ack);
   if (err)
@@ -225,7 +225,7 @@
 	    grub_priority_queue_pop (data->pq);
 
 	    if (file->device->net->packs.count < 50)
-	      err = ack (data, tftph->u.data.block);
+	      err = ack (data, data->block + 1);
 	    else
 	      {
 		file->device->net->stall = 1;