I have two Genuino 101 boards and running Ubuntu 16.04. I upload the same sketch file to both boards. For one board everything works fine, the board is recognized by the PC and performs as expected. However, the second board is not even recognized by the PC. That is, /dev/ttyACM0 does not appear.
I have tried hitting master reset and unplugging/plugging the USB back in. I've tried uploading other sketch files (e.g. Blink) and they work fine. It is only seems to be this particular sketch on this particular board that is causing problems.
The sketch file is a bit large to post, but I essentially modified this file by taking out all of the Port manipulation calls in order to make it compatable with the Intel Curie.