Can't make board work after unplug/reset.

Yesterday I made some changes (that'll be in the next Espruino version) so that the output buffer is a bit bigger, and if Espruino loads from flash it doesn't output the Espruino logo.

That means that your problem will go away, but that if you do:

var l = false;
setInterval("digitalWrite(LED1,l=!l);console.log('foo')", 200);

Then Espruino will still stop working after a while. I'm planning to do some work on flow control with the USART, so hopefully I'll roll an option for setting USB flow control into those changes.