Multi monitor problems

[flavm]

Hi,
I use "winvnc.exe -connect x.x.x.x" while on the other pc is running as "vncviewer.exe /listen -viewonly -quickoption 1"
I connect 2 PC on intranet and the server has 2 monitors, If I click on Viewer on "Full desktop/Switch monitor" button I have the following behavior:
1st click - I see only the primary display
2nd click - I see primary+secondary display
3rd click - I see only the primary display
4th click - I see only the primary display
5th click - I see primary+secondary display
....

The BIG problem is when I connect 2 PC over Internet with OpenVPN
I click many time on "Full desktop/Switch monitor" button but 99% doesn't work.
Some time if I click quickly many times and after a while one more time, it works.... but rarely.

I tried with version 1.0.9.6.2 and it works correctly.
I use UltraVNC from binaries unzipped folder, without install anything more.

Where is the problem?