With old Firmware version (January 2007) I have communicated with M250 via USB without problems. Today, I installed new Firmware Updater. On the base of it I upgraded my Sansa M250 to new Firmversion 1.41. I changed Settings to MSC (in the past, with changing settings to MSC I lost my MP3 files, today not!). At first, sight everything was without troubles. Once again, I changed Settings USB from MSC to Auto detect. I have tried to change my MP3 files in M250. I connected it with my computer via USB. Unfortunatelly, I can change anything. I received message: “The device is either stopped responding or has been disconnected”. The old MP3 files are in the M250. I can’t delete them or add new ones.
Try reformatting the device if you don’t mind deleting all your files.
Right click on the device under My Computer.
Take a look at the User Guide and Videos