Excuse me for my bad english but I'm french.
I have discover a Bug in RAdmin Viwer 3.
When you double-click on the computer to view, you have the prompt for the password, you enter it and you have the small window "Charging..." and the window of the remote computer.
So it's good.
But now if you enter the password at the prompt and you go in other windows (for example Windows Explorer, or Opera, or other) and you go back to the window of the remote computer that it's now charged. You can't use keyboard and mouse.
I have test on other computer and this problem appear too.