I have CentOS5.6x86_64 running under Server 2008R2 Hyper-V with the Linux Integration v2.1 and the Xen mouse packages installed. From a Win7x64 box with 2.0.3 the front window is often moved when opening the connection from the task bar. The front window in the session is relocated as far off-screen as possible. It's as if while opening the connection the window is selected, sent a drag message and moved to where the mouse is outside the VNC window. It should be waiting to get control until you actually click the mouse in the VNC window.
The functionality, sometimes called "sloppy focus," where the mouse has control without clicking on the window, actually seems to be a unique-to-TightVNC and desired feature for me. It may be nice to add it to the Connection Options screen to allow enable/disable if possible.
Ancient bug report, but personally I do not want this. So I "vote" for the connection screen option :)