diff --git a/src/lib/client/Client.cpp b/src/lib/client/Client.cpp
index 33048807..d50d1737 100644
--- a/src/lib/client/Client.cpp
+++ b/src/lib/client/Client.cpp
@@ -271,29 +271,38 @@ Client::leave()
 	m_active = false;
 
 	if (m_sendClipboardThread != NULL) {
-		StreamChunker::interruptClipboard();
+		StreamChunker::setClipboardInterrupt(true);
 		m_sendClipboardThread->wait();
+		delete m_sendClipboardThread;
 		m_sendClipboardThread = NULL;
-	}
-
-	m_condData = false;
-	m_sendClipboardThread = new Thread(
-								new TMethodJob<Client>(
-									this,
-									&Client::sendClipboardThread,
-									NULL));
-	// Bug #4735 - we can't leave() until fillClipboard()s all finish
-	Stopwatch timer(false);
-	m_mutex->lock();
-	while (!m_condData) {
-		if (!m_condVar->wait(timer, 0.5)) {
-			LOG((CLOG_WARN "timed out %fs waiting for clipboard fill",
-				(double) timer.getTime()));
-			break;
+		StreamChunker::setClipboardInterrupt(false);
+		for (ClipboardID id = 0; id < kClipboardEnd; ++id) {
+			if (m_ownClipboard[id]) {
+				m_sentClipboard[id] = false;
+			}
 		}
-		LOG((CLOG_DEBUG1 "leave %fs elapsed", (double) timer.getTime()));
 	}
-	m_mutex->unlock();
+	
+	if (m_sendClipboardThread == NULL) {
+		m_condData = false;
+		m_sendClipboardThread = new Thread(
+										new TMethodJob<Client>(
+											this,
+											&Client::sendClipboardThread,
+											NULL));
+		// Bug #4735 - we can't leave() until fillClipboard()s all finish
+		Stopwatch timer(false);
+		m_mutex->lock();
+		while (!m_condData) {
+			if (!m_condVar->wait(timer, 0.5)) {
+				LOG((CLOG_WARN "timed out %fs waiting for clipboard fill",
+					 (double) timer.getTime()));
+				break;
+			}
+			LOG((CLOG_DEBUG1 "leave %fs elapsed", (double) timer.getTime()));
+		}
+		m_mutex->unlock();
+	}
 
 	m_screen->leave();
 
@@ -301,7 +310,7 @@ Client::leave()
 		m_receivedFileData.clear();
 		LOG((CLOG_DEBUG "file transmission interrupted"));
 	}
-
+	
 	return true;
 }
 
diff --git a/src/lib/client/ServerProxy.cpp b/src/lib/client/ServerProxy.cpp
index 9c2b9c75..16459b43 100644
--- a/src/lib/client/ServerProxy.cpp
+++ b/src/lib/client/ServerProxy.cpp
@@ -364,8 +364,6 @@ ServerProxy::onClipboardChanged(ClipboardID id, const IClipboard* clipboard)
 	LOG((CLOG_DEBUG "sending clipboard %d seqnum=%d", id, m_seqNum));
 
 	StreamChunker::sendClipboard(data, data.size(), id, m_seqNum, m_events, this);
-
-	LOG((CLOG_DEBUG "sent clipboard size=%d", data.size()));
 }
 
 void
diff --git a/src/lib/server/ClientProxy1_6.cpp b/src/lib/server/ClientProxy1_6.cpp
index bdd0f23f..b4c33e82 100644
--- a/src/lib/server/ClientProxy1_6.cpp
+++ b/src/lib/server/ClientProxy1_6.cpp
@@ -58,8 +58,6 @@ ClientProxy1_6::setClipboard(ClipboardID id, const IClipboard* clipboard)
 		LOG((CLOG_DEBUG "sending clipboard %d to \"%s\"", id, getName().c_str()));
 
 		StreamChunker::sendClipboard(data, size, id, 0, m_events, this);
-
-		LOG((CLOG_DEBUG "sent clipboard size=%d", size));
 	}
 }
 
diff --git a/src/lib/server/Server.cpp b/src/lib/server/Server.cpp
index 3c9114e4..1f3bf3b2 100644
--- a/src/lib/server/Server.cpp
+++ b/src/lib/server/Server.cpp
@@ -509,9 +509,11 @@ Server::switchScreen(BaseClientProxy* dst,
 		// if already sending clipboard, we need to interupt it, otherwise
 		// clipboard data could be corrupted on the other side
 		if (m_sendClipboardThread != NULL) {
-			StreamChunker::interruptClipboard();
+			StreamChunker::setClipboardInterrupt(true);
 			m_sendClipboardThread->wait();
+			delete m_sendClipboardThread;
 			m_sendClipboardThread = NULL;
+			StreamChunker::setClipboardInterrupt(false);
 		}
 		
 		// send the clipboard data to new active screen
diff --git a/src/lib/synergy/StreamChunker.cpp b/src/lib/synergy/StreamChunker.cpp
index 380a37a3..d54839f3 100644
--- a/src/lib/synergy/StreamChunker.cpp
+++ b/src/lib/synergy/StreamChunker.cpp
@@ -17,6 +17,8 @@
 
 #include "synergy/StreamChunker.h"
 
+#include "mt/Lock.h"
+#include "mt/Mutex.h"
 #include "synergy/FileChunk.h"
 #include "synergy/ClipboardChunk.h"
 #include "synergy/protocol_types.h"
@@ -43,7 +45,7 @@ bool StreamChunker::s_isChunkingClipboard = false;
 bool StreamChunker::s_interruptClipboard = false;
 bool StreamChunker::s_isChunkingFile = false;
 bool StreamChunker::s_interruptFile = false;
-
+Mutex* StreamChunker::s_interruptMutex = NULL;
 
 void
 StreamChunker::sendFile(
@@ -144,10 +146,15 @@ StreamChunker::sendClipboard(
 	sendStopwatch.start();
 	
 	while (true) {
-		if (s_interruptClipboard) {
-			s_interruptClipboard = false;
-			LOG((CLOG_DEBUG "clipboard transmission interrupted"));
-			break;
+		{
+			if (s_interruptMutex == NULL) {
+				s_interruptMutex = new Mutex();
+			}
+			Lock lock(s_interruptMutex);
+			if (s_interruptClipboard) {
+				LOG((CLOG_DEBUG "clipboard transmission interrupted"));
+				break;
+			}
 		}
 
 		if (sendStopwatch.getTime() > SEND_THRESHOLD) {
@@ -177,6 +184,8 @@ StreamChunker::sendClipboard(
 
 	events->addEvent(Event(events->forClipboard().clipboardSending(), eventTarget, end));
 	
+	LOG((CLOG_DEBUG "sent clipboard size=%d", sentLength));
+
 	s_isChunkingClipboard = false;
 }
 
@@ -201,10 +210,24 @@ StreamChunker::interruptFile()
 }
 
 void
-StreamChunker::interruptClipboard()
+StreamChunker::setClipboardInterrupt(bool interrupt)
 {
-	if (s_isChunkingClipboard) {
-		s_interruptClipboard = true;
-		LOG((CLOG_INFO "previous clipboard data has become invalid"));
+	if (s_interruptMutex == NULL) {
+		s_interruptMutex = new Mutex();
+	}
+	Lock lock(s_interruptMutex);
+
+	if (interrupt) {
+		if (s_isChunkingClipboard) {
+			s_interruptClipboard = interrupt;
+			LOG((CLOG_INFO "previous clipboard data has become invalid"));
+		}
+		else {
+			LOG((CLOG_DEBUG "no clipboard to interrupt"));
+		}
+	}
+	else {
+		s_interruptClipboard = interrupt;
+		LOG((CLOG_DEBUG "reset clipboard interrupt"));
 	}
 }
diff --git a/src/lib/synergy/StreamChunker.h b/src/lib/synergy/StreamChunker.h
index b0bfb341..cca9442b 100644
--- a/src/lib/synergy/StreamChunker.h
+++ b/src/lib/synergy/StreamChunker.h
@@ -21,6 +21,7 @@
 #include "base/String.h"
 
 class IEventQueue;
+class Mutex;
 
 class StreamChunker {
 public:
@@ -37,7 +38,7 @@ public:
 							void* eventTarget);
 	static void			updateChunkSize(bool useSecureSocket);
 	static void			interruptFile();
-	static void			interruptClipboard();
+	static void			setClipboardInterrupt(bool interrupt);
 	
 private:
 	static size_t		s_chunkSize;
@@ -45,4 +46,5 @@ private:
 	static bool			s_interruptClipboard;
 	static bool			s_isChunkingFile;
 	static bool			s_interruptFile;
+	static Mutex*		s_interruptMutex;
 };