Incorrect longitude range in SQL queries

When I try to do a proximity search using the 98660 zip code and a circular range of 3000 miles, I return 0 results despite having several users with locations in that range. If I choose a smaller range, say 100 miles, they all appear in the result set.

Looking at the SQL query generated with the larger range, I noticed that the WHERE clause has some criteria that can't possibly be met, specifically regarding location.longitude. With this particular query, for instance, it's looking for:

location.longitude > 157.646527826 AND location.longitude < -43.0267078257

The location.latitude range is fine (location.latitude > 2.20655070794 AND location.latitude < 89.0979592921), but something's clearly up with the longitude calculation.