ERROR: Timed out waiting for Arduino 101 - anything I can do?

Press the reset button next to the USB port. (either one, the master reset is between the DC jack and USB ).

This will cause the Arduino 101 to reboot and enter DFU mode for 5 seconds if it is connected on USB. The download will proceed when the Curie enters DFU.

The IDE uses a baud-rate signal over USB. It is a virtual serial port, so baud rate doesn't matter. But when the host side (Arduino IDE) switches the baud rate to 1200, the board will reboot and enter DFU mode for download. If it gets stuck for some reason and misses the message to reboot, you can just hit the reset button and accomplish the same thing.