I'm running the latest version (1.1.x) on a RAMPS 1.4 single extruder setup.
The board boots up and displays the expected information, including correct temperatures for the extruder and bed, updating every few seconds.
I can connect using a serial terminal, and I'm able to change the display with a 'M117 Hello' command.
However, when I try an M105 command, the response is: 'ok T: ', then about 4 seconds later the LED on the RAMPS board starts flashing quickly (perhaps 10Hz), and no more commands are processed. The LCD stops updating. I can't even re-flash the board when it's in this state; I have to power it down and start again.
I've double-checked my config file, and the fact that the temperatures initially read correctly on screen leads me to think there's no obvious error there. Can anyone help?