<no values defined> means just what it says. There are no values in the value list. (Very helpful, I know.)
You'll typically see this when the value list is based on a table, but there are no values in the table. Check your source table for the value list and see if there are values in the field on which the list is based. That'd be the first thing to check.
If that's not the case, then check the relationship on which the value list is based and make sure it's valid from the current record. Are there related records from the current record? You can check this by temporarily dropping a portal on the layout from the same relationship and seeing if any records show up.
If neither of these is the case, let us know. Might be another weasel in the woodpile.
Ok, so that partially worked. One of my tables had all of its records deleted (I probably cloned another file, clearing all of its records, and forgetting that one of the tables' records provided a value list). However, one of my fields still isn't working...mostly...It works in one of my existing records but not in any others. How is that possible??
To hopefully clarify what I'm trying to do:
I have a table of personnel and a table of departments and institutions. When entering personnel I want to be able to select departments based on the previously selected institution. And like I said, one of my existing records allows me to do this. The others still say <no value defined> when I try to select department. Bizarre?
It sounds like your relationship isn't valid between the records where it's not working and the table on which the value list is based. Try dropping a portal using the same relationship onto the layout and then see what happens when you select a department.