I have a frustrating, intermittent problem. I have an iMac G5 2.0 mHz machine running Tiger 10.4.5, with an external FireWire drive. I have a large number of photo files stored on the external drive. For weeks, everything was fine, I could access the files as needed. Now several of the folders, when I open them. have only vanilla generic .jpeg icons rather than the thumbnail, and if I try and open them I'm told it may be corrupt, or may be in a format Preview cannot recognize. But some of the other photos, in the same folder even, do just fine. I can't help but think some type of cache file is corrupt -- but which one? How do I fix it? I've tried unmounting and remounting my FW drive, no luck. Also, sometimes, inexplicably, everything shows back up again and works fine. The same thing happened when I ran this drive off my eMac. What am I doing wromg?