I'm hoping the gurus here might have some ideas/suggestions.
First off, I feel I should mention that there really are no 'guru's here. This is simply a 'user' forum where other users try to help out. Having said that... the 250GB HDD Archos tablets have always been a bit tricky (and, from what I read never actually worked all the well).
So, instead of asking here I would highly recommend contacting/calling Archos directly and ask them about the best way to fix you device... especially, since at this point, it almost sounds like you've already totally wiped out the firmware on the device.
Unfortunately, I do not have any experience with the 250GB version, but I will assume it's pretty much similar to how starting over from total scratch is on the 8GB or 16GB versions. However, I would have to say the MOST IMPORTANT THING is to know just which firmware version you had on the device (before it got messed up).
The reason I say that is simply because there are far too many other weird problems with any of the 4.0.2x versions, and if you had 4.0.7 (or lower) you may NOT want to upgrade. And, if you did have 4.0.7 (or lower) and now do upgrade to ANY of the 4.0.2x versions there is NO WAY to ever downgrade back (other than learning how to 'root' your tablet and install an older 'rooted' version of the firmware.
I've always kind of wanted to get one of the Archos 250GB G9's, but since the hard drive in it is ONLY of any use for documents/photos/music/video... and it has less then 2GB to install any apps in... well, just was not anything I actually needed (I can always store all that other stuff on a sdcard or USB Thumb drive, so I've only got the Flash memory models simply for more app install space).
Wish I could help you out more. Maybe someone else will reply with better information to do so.