I just had the same thing happen to me. What a serious pita. But I have pretty much recovered. Thank you Jayshire & ZackMorris for your posts. It gave me an idea that seems to have worked.

Jayshire basically put the thought that the battery charge was the issue. I had drained the battery during normal use (and it seemed to drain faster then normal), so I went to reboot it (won't do that again) and was going to let it charge afterwords. But he mentioned that by switching batteries his machine came back to life.

ZackMorris mentioned that he could get it to boot up by using RD Mode enabled.

What I did was:
1. Reflashed the USA rom, (I couldn't flash the emc rom)
2. Switched to R&D Mode
3. Booted it up (YEAH!!!)
4. Let it sit charging connected to my computer.
5. A couple hours later - disabled R&D mode.
6. Now it is booting up again properly.

I lost all my customizations, because of step #1. ;-( Step #1 may not be needed, but it was performed while I was trying to recover, before I figured out a possible solution by reading the posts. So for completeness sake I'll list it. But I suspect it may not be needed.

It appears there is something in the boot up sequences (normal & battery charge) that checks the battery; and then somehow fails and it then reboots. RD mode bypasses that, allowing it to fully boot. Once it is booted, charging works! Charging appears to also be a "software" process of some sort, because I noticed when it was off and tried plugging it in it would go into the same reboot loop. So getting it booted up into the os in R&D mode is the key to allowing the battery to charge, which then once the battery is at a sufficient level, you can reboot and disable r&d mode.

Oh and emc flashing seems to require that the battery be fully charged; I still haven't be able to do it -- but my battery isn't fully charged yet. Is there some hotkey like the 'u' that puts the device into flash mode?

Nathan