
As Das has showed you,this happened some time ago.You need to keep all you songs backed up at other locations.I use 3 backup locations.And you ask how do I back up a Jamstudio file that is stored at Jamstudio only? Its a little work but it can be done.You will need a DAW or editor. You can try this free one:
http://www.downloadvance.com/audacity/ I use Mixcraft~5 myself. Now you will need to upload each file by itself as a WAV file to your PC.That way you will have music files for each Instrument in your song saved.
NOTE: This only works if you have an all access pass.