I am working on a project that uses the Arduino MKR1000 with ThingSpeak. While working on my code, I uploaded a bad sketch to the MKR1000. Every time that the board powers up, it starts running my bad code over and over and appears to be stuck in an infinite loop. I tried pressing the reset button, unplugging the USB cable, reboot my computer, reinstalling drivers, and unplugging the USB cable (for good measure). Nothing made the board responsive again. I found a forum post talking about the bootloader. The user mentioned that quickly pressing the reset button twice put the device into a good state by loading the bootloader. Success!