My SGS3 is recognised but does not connect or transfer files, not even a backup! My SGS3 is recognised -- but it does not connect or transfer files, not even a backup!

I have tried everything from numerous cables to different PCs &amp; even a Mac (because I'm a Mac user). I've used a PC to satisfy myself that it's not my Mac and nothing has worked.

Any suggestions? Should I contact samsung and say "Give me a new one"? But what good is that when all my files photos and music are on this that won't back up!!
I've had this issue with my S3 sometimes. Alternatively, what you could try is download and install the drivers from here: link. Or you could also try changing the USB mode from MTP mode to camera mode (from the notifications). Don't forget to restart after installing!