Sort Problem with Remote Database

I run an internet directory where users are allowed to search a database and then sort their search results by either of three fields labeled description, location and contact.

The search works fine but when they choose to sort by location, the list truncates itself. For example, a search produces 10 results, not sorted by location; clicking on sort by location will reduce the list to maybe 5 or 6 results that are now sorted, but missing 4 or 5 records.