Problem: Geocoder.BuildIndices fails when field name is greater than 10 chars (coverages only)
Solution or Workaround
If the BuildIndices method of the Geocoder is used to build an index on a field whose name is ten characters long, such as STREET_NAM, the BuildIndices method fails. This problem only affects ArcInfo coverages.
Field names longer than ten characters will cause an empty .gcd file (about 10Kb), which the IndexStatus method will consider Valid but cannot be used to geocode successfully.
Make sure the field names are less than ten characters long. This only applies to fields for which indices are built using Geocoder.BuildIndices.
Another solution is to convert the coverage with 10-character field names to a shapefile. Create a valid .gcd file based on the shapefile and copy or rename this file to use with the coverage.