Okay, it seems that I have fixed the Kobo version problem on my machine as follows.
Downloaded and installed BlackBerry Desktop Software (version 6.1.0.36 on an XP machine).
Started BBDS.
Turned off Playbook.
Plugged in (USB connection) to computer.
The red indicator on the Playbook comes on and a popup opens on the computer indicating that BBDS cannot communicate with the connected device.
Click on "Update�".
Popup gets replaced by a new popup (title: "Load BlackBerry Tablet OS", saying "Please wait while your BlackBerry Tablet OS is updated." After com.qnx.coreos.qcfm.os.factory.desktop software is downloaded to the computer, the popup indicates "Installing tablet software". Total time for download and install is about half an hour. Process finishes with another popup indicating "Your software update is complete. To continue using your tablet with the BlackBerry Desktop Software, you need to reconnect it after the update is complete.", and the Playbook reboots.
Another BBDS popup "Please disconnect the device. The device must be disconnected to complete the update process." happens while Playbook is rebooting.
Windows balloon appears on systray "BlackBerry Device Manager. Setup hasn't completed for the connected BlackBerry PlayBook tablet. Disconnect your device and finish setting it up (or complete the setup), then reconnect it to your computer."
Disconnect Playbook from computer.
On completion of boot process the Playbook is back at the start of the initialization (asking for Language and Country/Region). Complete initialization through to entering BB ID and password. Next page (Configuration) indicates "In order to finish configuring your PlayBook for your region additional files are required." Press Continue. 25MB of data is downloaded and installed. Playbook restarts without me even pressing the Restart button that is displayed. After restart, a blue screen is displayed titled "Software Update" with the text "Installation Successful", "PlayBook OS Update Version 2.0.0.7971". Swipe left to continue. Skip BB Bridge. Work through intro tutorial. Swipe left to continue and press "Done".
Open AppWorld and check MyWorld. Facebook, Need for Speed, and Tetris need upgrading, but I have "eBooks by Kobo version 1.4.2.1" and that's the version found with a search of AppWorld on the Playbook!! No more "endtouch" alerts. Still limited functions (no in-text links, no zoom, no in-text search) compared to the Kobo app on the iPhone, but it's back to the way it was.
Now to reload the tablet....
Notes,
- No prompt for backup before update occurs.
- This does not seem to work with the Mac version of BBDS (version 2.3.0 build 12). There is a point after you plug in the turned-off Playbook that offers you a "Repair�" button, but when I click "Repair" all that happens is that the Playbook continues through it's boot cycle and connects to the Mac.