Invalid Column name using Labor Adapter?

I’m using the Labor adapter to get some information I need on a separate screen. Can anyone think of any idea why:
optsl.PreLoadSearchFilter = “EmployeeNum = '” + employee + “’”;

works fine but:

optsl.PreLoadSearchFilter = “JobNum = '” + job + “’”;

gives me an error: Error accessing the database: Invalid column name ‘JobNum’.

Both fields are definitely in the table.

I can even use:
string jn = LA.LaborData.LaborDtl.Rows[rCount][“JobNum”].ToString();
to get the Job Number with the first one.

The problem is that the user will not know the EmployeeNum so they won’t be able to search by that but they will know the JobNum.