[Upgrading, Modifying and Unlocking] gabriel_agm:
Even being a SW and HW developer for a long time, I did had to spend some time to learn all the buzzwords in the "Android rooting" world to recover my Acer A200 tablet, so I'm sharing to save other people time:

My kid tried to guess the gesture password to play in my tablet, I don't know how many times, locking my Acer A200.

I tried google recovery, but the WiFi was off (and I could'nt turn on as the tablet was locked), so I went to the web to find a solution.

Factory reset seemed like a good one (turn device ON pressing power+down vol and switching the orientation key), it boots, then shows 'erasing user data', then hangs with an error:

Unrecoverable bootloader error (0x19000008)

Now the device is not booting, it get stuck on Acer logo after animation...

So I tried to use ADB to revert the damage, as indicated in one forum, but USB debug mode was not active when I did the factory reset.

ADB installation itself is unecessarily complicated, and as I cannot find a way to list the device in linux+adb ($>platform-tools/adb devices), even adding it to: /etc/udev/rules.d/51-android.rules (obtained with lsusb)

#Acer
SUBSYSTEM=="usb", ATTR{idVendor}=="0502", ATTR{idProduct}=="337d", MODE="0666", GROUP="plugdev"

It seems android isn't even booting to enable the debug bridge.

So I went to the "fastboot" as last resource (reboot using power+vol.down+switch.toggle), and did the command:

android-sdk-linux> platform-tools/fastboot oem unlock

I selected the "open lock" image and rebooted, now it shows: Bootloader v0.03.06-ICS(UnlockMode), but hangs in the same point.

So I downloaded a stock image from:

acertabletforum/stock-ics-recovery-image

Burned it using:

$> platform-tools/fastboot flash recovery /home/gaglocal/backup/acer/stockrecovery.img
sending 'recovery' (6144 KB)...
OKAY [ 1.882s]
writing 'recovery'...
OKAY [ 2.689s]
finished. total time: 4.571s

Same status after reboot.

So I've downloaded 'stock ROMs' from:

4shared/AcerStockROM

But when I try to write using fastboot:

error: update package has no android-info.txt or android-product.txt

So it seems this ROM is just for SDcard update (ie.: place the zip file as update.zip in the root of a fat32 sdcard, then boot using power+vol.down to perform the recovery process with it) but it fails and shows a dead android with a red triangle in the belly, not funny.

As the error that shows up when trying to issue the factory reset is after "erasing user data" I decided to do:

platform-tools/fastboot erase data
erasing 'data'...
FAILED (remote: (00030003))
finished. total time: 0.167s

This indicates this tablet has some HW misconfiguration issue. As some posted, I repeated the proccess a few times - no luck.

So I wrote the CWM 5.5.0.4 image from this forum, rebooted, and performed the sdcard recovery method again.

Same dead droid icon...

Finally I decided to erase the flash again, starting with the cache partition, using fastboot:

platform-tools/fastboot erase cache
erasing 'cache'...
OKAY [ 1.452s]
finished. total time: 1.453s

Finally, rebooted with the "factory reset" again and it worked!

At least i learned a lot without having to go to the Nvidia very-low level flashing process :)