I've had my iMac intel for three months, and spotlight has a tendency to spontaneously rebuild its index, unprovoked by me (it's done this three times), which means I can't use it for a few hours. Even worse, after the latest rebuild yestereday, it can't find anything at all. I type in a file name, and get zero results. If I do something to the file, however (open it or move it), then spotlight picks it up. Any ideas?