generally speaking if you just drop a data field on a footer it will show the value from the last record in your data set (or last row of a group in a GF).
You probably have NULL or " " values as a last row.
If you create a formula field as Maximum(table.somefield) and place that on the report footer you should get a value to show up.
Edited by DBlank - 10 Sep 2009 at 2:13pm