Hi
If I go to File-> Addons... then highlight the VNC server and edit the options and change the startup type to manual, click ok, click close, etc... then when I click on an online machine in the list I get a dialog box (red X icon in message box) saying "An invalid argument was encountered". After I click ok, a semi-transparent icon (same as the machine that I had clicked) follows my mouse around within the application's window until I click on a blank area in the window. Clicking an icon for oflline machines in the list seems to behave normally.
Tested on Windows Vista Home Premium, XP Pro Sp3