I pulled out one of my e-dongles to reprogram it with DMX for a test.
Now I remember that you definitely have to have the dongles power supply plugged in to make it program.
When you attempt to read the device without the power hooked up you will get 'device not found'.
Once I connected power to the dongle, restarted the PICkit 3 program, set the device type to 'PIC32MX795F512L' which is the device all the way at the bottom of the list I could read, erase, and reprogram the device. The check sum stayed at 000. Be sure the PICkit 3 is pointed (inport file) to the correct code file.