Index: scripts/broadcast-igmp-discovery.nse
===================================================================
--- scripts/broadcast-igmp-discovery.nse	(revision 29694)
+++ scripts/broadcast-igmp-discovery.nse	(working copy)
@@ -309,10 +309,12 @@
     local condvar = nmap.condvar(responses)
     -- Wait for the listening threads to finish
     repeat
-	condvar("wait")
 	for thread in pairs(lthreads) do
 	    if coroutine.status(thread) == "dead" then lthreads[thread] = nil end
 	end
+	if ( next(lthreads) ) then
+		condvar("wait")
+	end
     until next(lthreads) == nil;
 
     -- Output useful info from the responses