Can't connect no password dialog

[James Edwards]

I'm using Real VNC to manage my servers remotely and give a user access 
to maintain a Web site. On that server, randomly my user can't connect. 
She starts VNC viewer and the window to select the server appears, she 
selects the server and the selection window disappears but the password 
window never appears. I have to go over and locally access the server. I 
log the user account out and back in, the icon in the system tray turns 
from black to white and back on the system where the user tried to log 
in the password window (from the previous connection attempt, sometimes 
twice if she tried twice) appears and the user can then connect.

Anyone seen this before? Any fixes?

THANKS
Jim