diff -r 5b92bfa1abee src/devices/wifi/dcf-manager.cc
--- a/src/devices/wifi/dcf-manager.cc	Tue Jul 07 13:05:23 2009 +0200
+++ b/src/devices/wifi/dcf-manager.cc	Tue Jul 07 16:15:54 2009 +0400
@@ -433,7 +433,7 @@
 DcfManager::GetAccessGrantStart (void) const
 {
   Time rxAccessStart;
-  if (m_lastRxEnd >= m_lastRxStart) 
+  if (!m_rxing) 
     {
       rxAccessStart = m_lastRxEnd;
       if (!m_lastRxReceivedOk)