Hi all! Just want to chime in and say the above steps (reinstalling KUAL with the newest version + installing the
DevCerts update) unfortunately didn't work for me either on a Kindle 3G Keyboard. I continue to get the error "The title is not signed by a registered developer."
Before I was changing the time using USB Network to get back into KUAL and KOReader, but after updating KUAL I don't think that's an option anymore.
I'll keep my eye on this thread hoping for a fix. If anyone has any ideas or knows of steps I've missed, feel free to let me know!