Here's the answer to my own question. The solution was to modify Lucene.Net.Store.FSDirectory, by commenting out this unused line:
// Comments out by Corey Trager, Oct 2008 to workaround permission restrictions at shared host. This is not used.
// public static readonly System.String LOCK_DIR = SupportClass.AppSettings.Get("Lucene.Net.lockDir", System.IO.Path.GetTempPath());
There was one more security permission hurdle after that, and here's that workaround too. I don't understand why one way of getting the names of files in a directory would be blocked, and another way not blocked.
public override System.String[] List()
{
/* Changes by Corey Trager, Oct 2008, to workaround permission restrictions at shared host */
System.IO.DirectoryInfo dir = new System.IO.DirectoryInfo(directory.FullName);
System.IO.FileInfo[] files = dir.GetFiles();
string[] list = new string[files.Length];
for (int i = 0; i < files.Length; i++)
{
list[i] = files[i].Name;
}
return list;
/* end of changes */
// System.String[] files = SupportClass.FileSupport.GetLuceneIndexFiles(directory.FullName, IndexFileNameFilter.GetFilter());
// for (int i = 0; i < files.Length; i++)
// {
// System.IO.FileInfo fi = new System.IO.FileInfo(files[i]);
// files[i] = fi.Name;
// }
// return files;
}