My Mac G5 fails to reliably recognize the SanDisk Extreme USB card reader. It is connected via a powered hub. The behavior is the same when connected directly to the computer (no hub). Only occasionally is the reader recognized. Sometimes when recognized it will mount the icon on the desktop but refuses to open the file (it tries forever - the spinning beach ball). Is this a known problem with the Mac G5 OS 10.4.11? Does someone have a suggestion as to what I might try?