You begin a Spotlight search via the Find window (accessed by the Command-F command). You select to limit your search to a specific folder and to just “File Name.” After typing only two letters in the Spotlight text box, the results window surprisingly claims there are already no matches. This is surprising because you know that there are at least a dozen files that match the two letters you have typed. Clearly, something has gone awry.
In most cases, the cause is a corrupt Spotlight Index. The fix is easy: Rebuild the Index files.
One way to do this is to launch Terminal and type:
sudo mdutil -E / Enter your administrator’s password, when requested.
A more user-friendly (although not free) alternative is to use a shareware program called Spotless. With this utility, select the volume you were searching and click the “Delete 10.5 Index Files” button (assuming you are running Mac OS X 10.5).
With either alternative, after deleting the Index, Spotlight will shortly begin re-indexing your volume. This could take up to an hour or more, depending upon the size of your drive. After the reindexing is complete, searches should work properly again.