[users] Copy/Paste

[Mac McClain]

Sometimes when I open an existing spreadsheet I have a problem with copy and 
paste. I select an area with left click, then right click and get little menu 
to cut or copy. I select copy. Then go to another area (in same sheet) and 
select area with left click. Then when I do the right click the little menu 
still says cut or copy (paste is not an option).  Doesn't do this all the time 
and I have no idea what causes it or what to do to get rid of it. Any ideas?