Comment 3 for bug 1183658

I have the same problem described in the inital report, but I've noticed a partial solution. I have an htc one (not the one X).

For me, the files I'm attempting to transfer to my phone are located on a network computer. When attempting to copy and paste the files directly from the other computer to a directory on my phone (using nautilus), I got the "not supported by backend" error. The network computer is connected via ssh and the "Connect to server" feature on nautilus.

I then noticed that if I first transferred the files to the computer physically connected by cable to my phone, and then from that computer to the phone that I received no error. I confirmed this behavior with 3 separate file transfers.

My suggestion to others is to try placing the source file that you wish to copy in a different location (a separate partition, perhaps the root partition, etc).