FreeRunner does not boot although battery o.k.

[Alexander Kappner]

I use a FreeRunner (GTA02) with the OM2008 distribution. I turned it off
while it was connected to my desktop PC by pressing the power button for a
short time (the screen slowly faded as usual). The problem is that I have
**not been able to turn it back on** since then. It does absolutely nothing;
the screen remains black and no LEDs light up (not even the LCD backlight).
I connected it to the wall charger, tried to reboot it (both in NOR and in
NAND mode) and even removed the battery, left the device for a few seconds
and then put it back in. The battery is not discharged, a volt-meter shows
me that its voltage is 4.16V (well above its nominal voltage of 3.7V).
What can I do to bring my FreeRunner back to live?
The last thing I did was establishing the Ethernet-over-USB connection; my
phone behaved absolutely normal until I turned it off.
[Great phone btw]

Best regards
Alexander