I do not have the answer to this, but I have exactly the same problem with my SanDisk MP3 player. Presumably, part of the jack-socket not making proper contact with the earphone plug. I have also tried several earphones without success. If I press sideways on the plug wiith my thumb, the right hand sound channel comes back so long as I hold it pressed. But this is very awkward to do.
I wonder if this is a widespread problem with SanDisk products? Has anyone else experienced anything like it?
Nigel
March 2007