[ubuntu] screen doesn't update on remote desktop

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http://ubuntuforums.org – Very often when I connect to another computer on my LAN, the screen will sometimes not update. For example, I could click on 1 tab of 4 in FF and nothing will happen, I then have to click another tab before selcting the 1st one for it to appear again. ...or I can open a terminal and it doesn't appear, I then have to select a different window and go back to the terminal to see it. Any ideas what could cause this behaviour? (Hardware)