Make sure that both Specialists::pkRecordID and Specialists::Name are indexed. Check the storage options for your fields in Manage | Database.
A little known detail on indexing and "use values from a field" value lists:
When you specify two fields for this type of value list, only one field has to be indexed. The other can be unstored/unindexed though the results that you get in your valu list can change in some cases. The key requirement is that field that is visible or the field that is selected for sorting must be indexed. The other field does not actually have to be indexed. Recent versions of FileMaker will throw up an error message when the non visible or non sort field is not an indexed field, but you can actually ignore the warning and the value list will still list values.