Two previous solutions on FixYa! indicate the following to solve the issue:
Method 1:
1. Select 2nd option "Repair" or 3rd "Format the disk"
2. Connect 605 to PC using USB wire and find the Driver named "a605" or similar words
3. Copy a firmware to the ROOT directory on the driver mentioned above
4. Keep the USB connected and select "OK" on 605
5. Re-calibrate the screen under Display menu on 605.
Method 2:
1) connected via USB and got all my Picture, Videos and Music to a safe place.
2) Downloaded firmware update.
fouund it here -
http://www.downloadplex.com/Drivers/Firmware/Archos/Download-Archos-605-Wifi-4GB-Firmware-2.1.04_109044.html
3. Copied update to root of archos drive and rebooted
4. Archoes installed the update and rebooted and came up to desktop again
5. reinstalled plugins (thank god I saved them) copied plug-in to root.
6. Back on the road again