I'm looking at someone else's worksheet and am hoping to add some formulae of
my own to massage their data. However something rather odd is happening.

For some unknown reason, formulae that I enter in cells to the left of a
particular column (call it X) would work as one would expect. But if I enter
the exact same formulae (say by dragging the cell to the right) in column X
and all columns to the right of it, they all return zero. The formulae I'm
talking about can be as simple as =A1 and they still return zero when clearly
the values should not be zero.

What possibly could be going on? And of course, how can I resolve it? When I
open the sheet, there is a warning about circular references. Thanks.