HI Perry,
Do your fields that you selected appear in the dropdown list under heading "Search work items satisfying search key field conditions:"? (The default value to the drop down is "No search field specified")
You'll only see one dropdown list, and the fields to allow entering search criteria only appears once you have selected the field to use. This, I presume, enables different behaviour for different data types.
If they do not appear in the dropdown list in the first place, then there is something wrong with the configuration of those fields - redo the lot and save your process map again on the server and see if that works. Oh - and run a test process or two, filling those fields, so the database has some data for the fields, too.
Hope this helps,
Sanna