Ultra encoding + Track Remote Cursor Locally combination of settings will cause vnc viewer to hang.
1) Configure VNC viewer to use the Ultra encoding.
2) Cursor handling mode must be set to Track Remote Cursor Locally
3) Connect to a VNC server. In order to reproduce the issue some screen activity should by happening on the server side.Just play c:\windows\clocks.avi in the Media Player for example.
4) Hover mouse cursor over the viewer window.
I'm getting hang within seconds. It seems like there is a deadlock that occurs during screen updates processing and cursor updates processing.