It turns out now that when I turn on the board, none of the LEDs blink link before, both using the FTDI cable and using a 2A 5V power source. I've tried to re-flash nodeMCU, with no luck (using OS X). This is also after putting a 220 ohm resistor between pin #0 and GND; I verified that there was 5V between V+ and GND, so it's at least getting powered. I also can't flash anything via Arduino.
Here's the output from trying to flash the board using esptool:
Any ideas what's going on? Is the board defective? Thanks.➜ ~ ls /dev/tty.*
/dev/tty.Bluetooth-Incoming-Port /dev/tty.usbserial-AL00A3UC
➜ ~ /usr/local/bin/esptool.py -p /dev/tty.usbserial-AL00A3UC --baud 460800 write_flash --flash_size=8m 0 ~/Downloads/nodemcu-master-8-modules-2016-10-17-01-41-36-integer.bin
esptool.py v1.1
Connecting...
A fatal error occurred: Failed to connect to ESP8266