No longer able to copy cells
 

I use Excel 2000. A few weeks ago I began to have a problem when I would
highlight a cell, right click copy, select a long column, and then paste. It
would appear as if I had never ever originally highlighted the original cell.
What I have now noticed is that when I highlight a cell that it will only
stay highlighted for a short time, 10-15 seconds. Any ideas would be
appreciated.
Thanks,
--
Barry Livingston