You have a broken display profile. A bad profile may affect different applications differently; and some applications aren't color managed at all and don't use the profile.
Recalibrate to make a new profile, or if you don't have a calibrator use sRGB until you get one. Go to Control Panel > Color Management > Devices:
Relaunch Lightroom so that it can pick up the new profile at startup.
This sounds like a corrupted monitor profile or at least one that LR is finding unpalatable. If your monitor is calibrated, recalibrate. And if given the choice, select to make a V.2 profile. LR 3 does not support V.4 profiles and PSE may also have problems with them. If you have not calibrated your monitor, check your OS display settings to see if it is using a generic profile made by the monitor manufacturer and installed by the driver. LR sometimes finds these canned profiles indigestible. To test whether it is in fact a display profile problem, make sRGB your OS display default. If LR's display improves, you will have your answer.
N. B., setting sRGB as the display default in effect cancels LR and PSE color management. It is only a temporary test, not a solution.
Dorset Photographer wrote:
If I select Adobe RGB colour space within the camera, will the images be displayed accurately in non-Adobe applications or printers?
Yes but only if the other applications are color managed (understand ICC profiles for display and printer).
Thank you 21 for solving the problem. The colour profile was set to 1905FP.icm which is logical as the monitor is a Dell 1905P. I assume this file is corrupted. When I Added sRGB and set it as the Default profile, the colour was immediately rendered accurately in LR3 and PSE10. I suppose I could look for the uncorrupted 1905.icm profile but as I am taking delivery of a new Dell XPS 8700 today I may not spend too much time looking. With Windows 8.1 to get my head around I'm not likely to have much time in the foreseeable future. I hope the new PC will solve my Samsung-Kies synchronisation problems under XP. Many thanks.
Thanks for also supplying the correct answer.
Dorset Photographer wrote:
When I Added sRGB and set it as the Default profile, the colour was immediately rendered accurately in LR3 and PSE10.
It fixed the ugly preview but please don't think it's accurate. It will only move towards that goal by calibrating and creating a custom ICC display profile that defines your display system.
If you view an image in Photoshop or Lightroom using that generic sRGB profile, then view the same image in a non ICC aware application as I discussed, they will not match. That is because LR is ICC aware and uses the actual display profile (which in your case is better but not correct in terms of describing your Dell and that is why they provided another almost equally canned profile). Non ICC app's just send the numbers to the display which is quite different from what LR and Photoshop does.