I may be well off target here, but maybe Windoz has got its knick's in a twist. Try a reboot and see if it returns.
If not, maybe a bit more info on what your trying to do may be helpful. Are you trying to copy and paste from within the same document or different ones?
Thanks chaps, problem solved after my son was asked this question. Hed been playing about with the PC and altering things without telling me. I now have all my settings in photo editing soft ware back to normal to, as well as the scanner soft ware he so kindly played about with.
Windows Xp is a good operating system but only if you know how to use it. Always create a system restore point, then when things go wrong, easily sorted out just restore back to when everything was working correctly.
Also a good program in Xp is Windows Compatability Mode you can use it to install software that is not digital signed and programmes written for earlier windows platforms like ME 2000 98 ect. work like printers scanners ect