If you reset rusEfi while serial-over-USB is connected, you cannot connect it again till you reset rusEfi one more time.
Looks like this issue is reproducible with just ChibiOS demo code - so it's not our issue http://forum.chibios.org/phpbb/viewtopic.php?f=16&t=1727
Current workaround:
close dev console, unplug micro USB cable
reset MCU one more time
connect micro USB, open dev console
Current workaround:
1) close dev console
2) hit 'reset' on the discovery
3) wait till the windows 'device connected' sound if you have this sound
4) open dev console