diff --git a/client/net_xfer.C b/client/net_xfer.C
index ac6641a456..fa480ab779 100644
--- a/client/net_xfer.C
+++ b/client/net_xfer.C
@@ -128,7 +128,7 @@ int NET_XFER::open_server() {
             NetClose();
             return -1;
         }
-        if (WSAAsyncSelect( fd, g_myWnd->GetSafeHwnd(), WM_TIMER, FD_READ|FD_WRITE )) {
+        if (WSAAsyncSelect( fd, g_myWnd->GetSafeHwnd(), g_myWnd->m_nNetActivityMsg, FD_READ|FD_WRITE )) {
             errno = WSAGetLastError();
             if (errno != WSAEINPROGRESS && errno != WSAEWOULDBLOCK) {
                 closesocket(fd);
diff --git a/client/win/win_util.h b/client/win/win_util.h
index 4890831d06..3e47e24934 100755
--- a/client/win/win_util.h
+++ b/client/win/win_util.h
@@ -10,3 +10,4 @@ int UtilInitOSVersion( void );
 #define START_SS_MSG		"BOINC_SS_START"
 #define SHOW_WIN_MSG		"BOINC_SHOW_MESSAGE"
 #define RUN_MUTEX			"BOINC_MUTEX"
+#define NET_ACTIVITY_MSG    "BOINC_NET_ACTIVITY"
diff --git a/client/win/wingui_mainwindow.cpp b/client/win/wingui_mainwindow.cpp
index 30db04a53c..13a6a538a5 100755
--- a/client/win/wingui_mainwindow.cpp
+++ b/client/win/wingui_mainwindow.cpp
@@ -108,6 +108,7 @@ CMainWindow::CMainWindow()
 
 	m_nScreenSaverMsg = RegisterWindowMessage(START_SS_MSG);
 	m_nShowMsg = RegisterWindowMessage(SHOW_WIN_MSG);
+	m_nNetActivityMsg = RegisterWindowMessage(NET_ACTIVITY_MSG);
 }
 
 //////////
@@ -918,6 +919,9 @@ LRESULT CMainWindow::DefWindowProc(UINT message, WPARAM wParam, LPARAM lParam)
 	} else if(m_nScreenSaverMsg == message) {
 		m_pSSWnd->SetMode(MODE_FULLSCREEN);
 		return 0;
+	} else if(m_nNetActivityMsg == message) {
+		while(gstate.net_sleep(0));
+		return 0;
 	}
 
 	return CWnd::DefWindowProc(message, wParam, lParam);
diff --git a/client/win/wingui_mainwindow.h b/client/win/wingui_mainwindow.h
index f3ab857f8e..eb381a2122 100755
--- a/client/win/wingui_mainwindow.h
+++ b/client/win/wingui_mainwindow.h
@@ -88,6 +88,7 @@ public:
 	void					MessageUser(char*,char*,char*);
     BOOL					IsSuspended();
     BOOL					RequestNetConnect();
+	UINT					m_nNetActivityMsg;		// ID of net activity message
 
 protected:
 	CMenu					m_MainMenu;				// window's main menu