I have a tightvnc viewer problem if I shadow on devices with the operating system ThinOS (for example http://wyse.com/products/cloud-clients/thin-clients/C10LE).
The shadowed picture is warped and has a wrong color. I used tightvnc-viewer version 2.7.10 on an Windows 7 64bit system. With other vnc viewers there is no problem.
Please find attached the viewer log with verbosity level 9.