Under Windows Vista SP2 running UltraVNC 22.214.171.124.2 (and earlier), when a user access control permissions dialog comes up, it often (but not always) causes Chicken 2.2b2 to drop the connection and present an "Unknown message type N" message, where for N I've seen -1, 4, 6 and 107. After responding to the dialog, the same thing happens (dropped connection, "Unknown message type" message from Chicken), though the number may be different. The screen is sometimes updated to display the UAC dialog before the connection is dropped, sometimes not. "Unknown message type 4" and "Unknown message type 6" are the most common.
No UltraVNC server options are set (right-click system tray icon, "Properties"). In particular, the polling, "System HookDLL" and "Video Hook Driver" aren't enabled. As for admin properties, UltraVNC is set to remove Aero and the wallpaper on connection, and "Blank Monitor on Viewer Request" is enabled. Most other options are unchecked.
OS X 10.6.8 (client)
Vista SP2 (server)
UltraVNC 126.96.36.199, 188.8.131.52.2