Is it possible to only share a single window or application over VNC? This would be useful for sharing only one aspect of a computer with another viewer.
From Microsoft Windows preferably.
Try changing to a different VNC. I know UltraVNC only supports the primary monitor although the last time I used it (1.0.8) it did not play nice with Windows 7.
edit: sorry I misunderstood your post. On the first reading I assumed you had a dual monitor setup and only wanted to share one screen. I don't know of a VNC client that can share a single window although you could try Microsoft SharedView.