I had the exact same problem as you and just couldn't figure it out - in fact, it was your post that attracted my attention on the net!
This sounds simple, but perhaps it will work - it did for mine. A few days ago, plugged in the Micro for recharging from the charger in the wall and it seemed to charge, as the indicator on the micro in the top right of the screen was flashing, but the micro wasn't 'breathing' (y'know, the way they glow on and off when they charge). Anyhoo, I wasn't too concerned about the glowing, and thought it had charged OK. Came to turn it on the following day and it just WOULD NOT boot up. Plugged it back into the charger and tried turning it on - immediately went to the recovery screen and I thought 'uh oh'. Tried all of the options it gives - reboot, reformat etc and nada. It wouldn't even finish the recovery process and the whole thing made me think the hard drive had died, though I hadn't dropped it or anything. Baffled.
I thought I'd change tack and before I took it apart, would look for the simple solution - battery and charger. Battery is OK - tried it in another Zen - but the CHARGER is NOT working. - I tried it with another micro and that micro wouldn't 'glow' either. So, in essence, the reason the Micro appeared dead was because there was absolutely no life whatsoever in the battery, because it hadn't been properly charged for yonks. Doesn't wholly explain why it went into recovery mode when plugged into the charger, BUT, once I'd replaced the charger and charged up the Micro, she started up again like nothing had ever happened.
I know it seems silly, but perhaps start with that before you take it to bits? I was ready to hack away at the Micro, but thought I'd try this first - and it worked!