I have inherited a spreadsheet and encountered a problem I have never seen
before. In the spreadsheet there is the following sum in cell k159

=+K5+K19+K33+K47+K61+K75+K89+K117+K131+K145+K103

When I copy this sum to cell k166 the sum looks like this

=+K12+K26+K40+K54+K68+K82+K96+K124+K138+K152+K110

Now this looks as it should, however rather than getting the sum of the
cells above I get the same answer as the first sum which is incorrect.

I have looked at the way the cells are formatted, checked the sum and I have
been unable to workout why this is happening. The other thing that happens is
when I key the sum to the second set of cells above I get 0 as the answer. It
is as if excel cannot see the cell contents.