Another method (not that much sophisticated ), but worked for me when I was hit by this.
plug in, let charge for a minute or so (as long as LED blinks), shut down via 8 second long power button push. Do this for two or three times and it should have enough (watch out) juice to load the second stage kernel and charge normally.
To get to second stage kernel, just plug USB out and directly in again.

--edit
Just seen juiceme's advice and I have to add that this is only possible with ubiboot-02.

--edit2
@juiceme
above commands would be nice to have in a small script (maybe /boot/boot?) bundled already and provided in ubifs.