Originally Posted by zkat
When I reboot it into HID mode, I can see the HID device with 0x15a2. When I press 'start' on the MfgTool using the Kindle fastboot profile, the progress bar on the tool seems to complete, but the button stays red/"Stop", and the device status changes to 'Please connect device' (again, in the mfgtool).
Unfortunately, I don't really have the means right now to get serial port access.
That is normal behavior! Until you stop MfgTool, it keeps looking for another kindle to send u-boot to. You should stop it.
The REASON that it cannot see a kindle in USB Downloader mode (0x15a2/0x0052) is BECAUSE the kindle changed to fastboot mode (0x1949/0xd0d0).
You should use the fastboot tool WITHOUT unplugging the kindle from the USB port, which can make it drop out of fastboot mode.