I have a large data set which I am trying to summarize. Basically I am
trying to sum the weight of fish caught by site. It shows the counts
correctly but everytime I try to switch the calculation to sums, it displays
0 for all of the cells which I know not to be correct. Does anyone know what
is going on? I have been trying to figure it out all day.

If it helps, I am using Excel 2002.