I often have the same problem when trying to connect from Win7 x86 Sp1 to a Mac OSX 10.6.8 host machine.
Connection establishes successfully but the remote desktop does never appear.
Only a reboot helps.
Here's an excerpt of the host logfile:
2011/06/30 09:32:53.264 2302686379328 G0 Using IPC-Port 6039
2011/06/30 09:32:53.264 2302686379328 G0 UpdateOnlineState newOnlineValue 0
2011/06/30 09:32:53.265 2302686379328 G0 Starting intra process connection
2011/06/30 09:32:53.270 2302953318400 G0 CInterProcessNetwork::SetDyngateIDforSession() id=676634xxx session=501 ptype=2
2011/06/30 09:32:53.271 2302953318400 G0 UpdateOnlineState newOnlineValue 0
2011/06/30 09:32:53.272 2302953318400 G0 Received Control_InitIPC_Response processtype=1
2011/06/30 09:32:53.273 2302953318400 G0 Received Control_InitIPC_Response runningProcesses=3
2011/06/30 09:32:53.274 2302953318400 G0 Control_InitIPC_Response: all processes 3 completely initialized
2011/06/30 09:32:53.517 2302686379328 G0 accelerated display found: 188837368 (1280x1024)
2011/07/04 09:02:34.926 14082954383360 D0 TeamViewer_Desktop Start, PID=1408
2011/07/04 09:02:35.082 14082954383360 D0 Opening local TCP connection to 127.0.0.1:5939
2011/07/04 09:02:35.083 14082954383360 D0 Local TCP connection established
2011/07/04 09:02:35.088 14082954383360 D0 Received Control_InitIPC_Response processtype=1
2011/07/04 09:02:35.089 14082954383360 D0 Received Control_InitIPC_Response runningProcesses=5
2011/07/04 09:02:35.089 14082954383360 D0 Control_InitIPC_Response: all processes 5 completely initialized
2011/07/04 09:02:38.592 14082954383360 D0 Received Control_InitIPC processtype=2
2011/07/04 09:02:38.400 14092686379328 G0 Opening local TCP connection to 127.0.0.1:5939
2011/07/04 09:02:38.469 14092686379328 G0 Local TCP connection established
2011/07/04 09:02:38.503 14092686379328 G0 Received Control_InitIPC_Response processtype=1
2011/07/04 09:02:38.504 14092686379328 G0 Received Control_InitIPC_Response runningProcesses=7
2011/07/04 09:02:38.593 14092686379328 G0 Received Control_InitIPC_Response processtype=4
2011/07/04 09:02:38.595 14092686379328 G0 Control_InitIPC_Response: all processes 7 completely initialized
2011/07/04 09:02:38.732 14092686379328 G0 accelerated display found: 188837368 (1280x1024)
2011/07/04 09:02:39.207 14092686379328 G0 Search crashLog
2011/07/04 11:12:39.481 14092954383360 G0 Timeout for master message.
2011/07/04 11:12:39.503 14092954383360 G0 Timeout for master message.
2011/07/04 11:12:39.504 14092954383360 G0 Timeout for master message.
2011/07/04 12:56:38.154 14082954383360 D0 Connection incoming, sessionID = -1209809892
2011/07/04 12:56:38.155 14082953850880 D0 CLogin::run()
2011/07/04 12:56:38.155 14082953850880 D0 CLogin::NegotiateVersionServer()
2011/07/04 12:56:38.269 14082953850880 D0 CLogin::AuthenticateServer()
2011/07/04 12:56:40.716 14082953850880 D0 CLogin::run(): ConnectionMode == 1
2011/07/04 12:56:40.717 14082953850880 D0 CServerThread::Factory(PseudoSocket)
2011/07/04 12:56:40.721 14082953850880 D0 CGGetActiveDisplayList: displayCount == 0, 0
2011/07/04 12:56:40.721 14082953850880 D0 Monitor number 0 not available. Selected Monitor 0.
2011/07/04 12:56:40.722 14082953850880 D0!! CGGetActiveDisplayList: numDisplays == 0, Errorcode=22
2011/07/04 12:56:40.722 14082953850880 D0 CGGetActiveDisplayList: 0
2011/07/04 12:56:40.723 14082955448320 D0 DesktopThread started
2011/07/04 12:56:40.723 14082953850880 D0 CLogin::run() leave
2011/07/04 12:56:40.724 14082955980800 D0 ServerThread started
2011/07/04 12:56:40.725 14082955448320 D0!! No active displays found!, Errorcode=22
2011/07/04 12:56:40.725 14082955448320 D0!! InitDesktop failed, waiting 1 second, Errorcode=22
2011/07/04 12:56:40.862 14092953318400 G0 ServerThread connected to 324616008, client version is 6.0.10722 P, OS=13
2011/07/04 12:56:40.863 14082955980800 D0 ServerThread connected to 324616008, client version is 6.0.10722 P, OS=13
2011/07/04 12:56:41.726 14082955448320 D0!! No active displays found!, Errorcode=22
2011/07/04 12:56:41.726 14082955448320 D0!! InitDesktop failed, waiting 1 second, Errorcode=22
2011/07/04 12:56:42.727 14082955448320 D0!! No active displays found!, Errorcode=22
2011/07/04 12:56:42.727 14082955448320 D0!! InitDesktop failed, waiting 1 second, Errorcode=22
2011/07/04 12:56:43.728 14082955448320 D0!! No active displays found!, Errorcode=22
2011/07/04 12:56:43.729 14082955448320 D0!! InitDesktop failed, waiting 1 second, Errorcode=22
2011/07/04 12:56:44.729 14082955448320 D0!! No active displays found!, Errorcode=22
2011/07/04 12:56:44.730 14082955448320 D0!! InitDesktop failed, waiting 1 second, Errorcode=22
2011/07/04 12:56:45.731 14082955448320 D0!! No active displays found!, Errorcode=22
2011/07/04 12:56:45.731 14082955448320 D0!! InitDesktop failed, waiting 1 second, Errorcode=22
2011/07/04 12:56:46.732 14082955448320 D0!! No active displays found!, Errorcode=22
2011/07/04 12:56:46.732 14082955448320 D0!! InitDesktop failed, waiting 1 second, Errorcode=22
2011/07/04 12:56:47.733 14082955448320 D0!! No active displays found!, Errorcode=22
2011/07/04 12:56:47.734 14082955448320 D0!! InitDesktop failed, waiting 1 second, Errorcode=22
2011/07/04 12:56:48.170 14092954383360 G0 Timeout for master message.
2011/07/04 12:56:48.734 14082955448320 D0!! No active displays found!, Errorcode=22
2011/07/04 12:56:48.735 14082955448320 D0!! InitDesktop failed, waiting 1 second, Errorcode=22
Edit:
First it only happened when the Mac had a password required after the screen saver becomes active.