The problem is as follows:
First, the winvnc A PC has installed xp.
In B PC in win7x64 PC it has connected to the first viewer xp. (Share the server checked)
In C PC has connected to the second viewer in Win8x64 PC with xp.
If you attempt over the top job in the last two or three connected PC Viewer it is shown with a gray screen.
Note: In 22.214.171.124 winvnc server does not occur.