We have had a few different reports of this and I can suggest two ways to resolve the problem.
1) It is normally related to the version of the VNC server and re-installing the VNC server or (more often) upgrading it to the latest version will usually resolve the problem
2) It only happens when making direct TCP/IP connections. By going to Options in Mobile Desktop you can change the connection method from Direct Carrier TCP/IP to BIS - Internet Browser (if you do not have a BlackBerry Enterprise Server) or to BlackBerry Enterprise Server/MDS (if you do).
A connection through BIS is comparable in speed to a direct TCP/IP connection.
If you are still having problems please contact us directly at