"I suspect that you'll find that your column names will include the to_char function:"

Thanks, astroboy! This is exactly what was happening and I don't know why I didn't think to just print out the hash to investigate. (I guess it had something to do with getting less than 6 hours of sleep the night before.) The SELECT statement looked like this:

SELECT granule_name, path, to_char(start_date, 'yyyymmddhh24miss'), to
+_char(stop_date, 'yyyymmddhh24miss'), byte_size, num_passes, browse_a
+vail FROM $invName WHERE $pclause $sclause $suffix
[download]

The key/value pairs look like this:

granule_name f15_grid_2009.243_dayAD.eos
path 2009/f15_grid_2009.243_dayAD.eos
to_char(stop_date,'yyyymmddhh24miss') 20090901004308
to_char(start_date,'yyyymmddhh24miss') 20090831000749
byte_size 4888111
num_passes 29
browse_avail Y
[download]