There have been some comments about bricked Bluetooth dongles after flashing Frontline firmware on it. FTE seems to have modified the firmware layout of the Frontline dongles which will leads to bricked Bluetooth dongles when you try to flash them with this firmware.
Till now I didn’t had the time to take a closer look on this. Anyway for unbricking your dongles have a look at this post. I used the SPI interface and a Bluetooth Casira Development board to unbrick the dongle. Unfortunately you need the quite expense develpment board and the software to fix the dongle, but in theory it should be possible to fix this with homebrew software and hardware.
If a have some free time during the next month I will take a closer look on this topic.