Index: /trunk/FACT++/src/Connection.cc
===================================================================
--- /trunk/FACT++/src/Connection.cc	(revision 12539)
+++ /trunk/FACT++/src/Connection.cc	(revision 12540)
@@ -198,5 +198,6 @@
     // functions directly from any other place then Handlers, use
     // PostMessage instead
-    fOutQueue.pop_front();
+    if (!fOutQueue.empty())
+        fOutQueue.pop_front();
 
     if (fOutQueue.empty())
Index: /trunk/FACT++/src/ConnectionUSB.cc
===================================================================
--- /trunk/FACT++/src/ConnectionUSB.cc	(revision 12539)
+++ /trunk/FACT++/src/ConnectionUSB.cc	(revision 12540)
@@ -205,5 +205,6 @@
     // functions directly from any other place then Handlers, use
     // PostMessage instead
-    fOutQueue.pop_front();
+    if (!fOutQueue.empty())
+        fOutQueue.pop_front();
 
     if (fOutQueue.empty())
@@ -214,5 +215,5 @@
     }
 
-    // AsyncWrite + Deadline
+     // AsyncWrite + Deadline
     AsyncWrite(ba::const_buffers_1(fOutQueue.front().data(), fOutQueue.front().size())/*, &ConnectionUSB::HandleSentData*/);
     AsyncWait(fOutTimeout, 5000, &ConnectionUSB::HandleWriteTimeout);