diff -r 5a6ac1d1bc0e -r ddb02fd788ec Hardware/Heatmaster/Heatmaster.cs
--- a/Hardware/Heatmaster/Heatmaster.cs	Tue Mar 15 21:54:56 2011 +0000
+++ b/Hardware/Heatmaster/Heatmaster.cs	Tue Mar 15 22:00:31 2011 +0000
@@ -16,7 +16,7 @@
 
   The Initial Developer of the Original Code is 
   Michael Möller <m.moeller@gmx.ch>.
-  Portions created by the Initial Developer are Copyright (C) 2010
+  Portions created by the Initial Developer are Copyright (C) 2010-2011
   the Initial Developer. All Rights Reserved.
 
   Contributor(s):
@@ -265,7 +265,7 @@
       if (!available)
         return;
 
-      while (serialPort.BytesToRead > 0) {
+      while (serialPort.IsOpen &&  serialPort.BytesToRead > 0) {
         byte b = (byte)serialPort.ReadByte();
         if (b == 0x0D) {
           ProcessUpdateLine(buffer.ToString());