diff -r 42fbd117c3e3 -r eefccfa312ef master/master.c
--- a/master/master.c	Fri Jul 08 15:31:46 2011 +0200
+++ b/master/master.c	Thu Jul 21 18:25:38 2011 +0200
@@ -841,6 +841,8 @@
         ec_datagram_t *datagram /**< datagram */
         )
 {
+    ec_datagram_t *queued_datagram;
+
     switch (datagram->state) {
         case EC_DATAGRAM_QUEUED:
             datagram->skip_count++;
@@ -855,12 +857,28 @@
             break;
 
         default:
-            list_add_tail(&datagram->queue, &master->datagram_queue);
+            break;
+    }
+
+    /* It is possible, that a datagram in the queue is re-initialized with the
+     * ec_datagram_<type>() methods and then shall be queued with this method.
+     * In that case, the state is already reset to EC_DATAGRAM_INIT. Check if
+     * the datagram is queued to avoid duplicate queuing (which results in an
+     * infinite loop!). Set the state to EC_DATAGRAM_QUEUED again, probably
+     * causing an unmatched datagram. */
+    list_for_each_entry(queued_datagram, &master->datagram_queue, queue) {
+        if (queued_datagram == datagram) {
+            datagram->skip_count++;
+            EC_MASTER_DBG(master, 1, "Skipping re-initialized datagram %p.\n",
+                    datagram);
             datagram->state = EC_DATAGRAM_QUEUED;
-            break;
-    }
-}
-
+            return;
+        }
+    }
+
+    list_add_tail(&datagram->queue, &master->datagram_queue);
+    datagram->state = EC_DATAGRAM_QUEUED;
+}
 
 /*****************************************************************************/