When I open an image in the Develop module in Lightroom it appears in the working area as a highly coloured/posterized image almost as if there is a histogram warning. Can anyone advise on how to turn this off?
If you are talking about the clipping, you may turn it off/on by pressing the "J" key.
Also if it does not help, please attach a screen shot of the image from Lightroom.
Turn the graphics processor option off in the preferences.