I have a iPod 160GB model MC297 Mac2.0.4 that I use as a hard disk via USB2 to securely carry data between my MacbookPro at home and my new iMac 3.5 GHz Intel Core i7 with 32 GB RAM at work, both running OS 10.9.5. The mounted disk has recently started erratically dropping the connection with either Mac, either after sleep or just during a pause in use, even with documents open. The iPod icon disappears from Desktop and menus. This then requires physical disconnection and re-connection to re-mount, and then a 'Save As' to save the document. It is very easy to lose data, if one does not notice the mount has been lost as Save does not save and gives no warning. I have reset the iPod and put it back to factory settings: same problem. What can I do to solve the problem?