Has anyone unlocked a Navman MY400LMT?

GPS freezes on startup page and doesn't load maps. This all started to happen after a failed update.
Because of this Windows doesn't recognize it as an USB external device so I can't see any files.
Tried installing MioPocket as frontend for Windows CE on SD card but haven't had any success. I'd like to try and access files on this device to try and repair original files.

Anyone had any luck unlocking these devices?

Thanks,

It looks like you don't need to unlock the device, but flash its firmware.

Is it possible to flash its firmware if Windows doesn't recognise the device as an external USB drive?

Yes.Firmware is installed from the SD card.

Thank you Oleg69. Sorry for late reply, haven't been near PC lately.
Will try and get firmware update for device, although Navman Support tells me it's no longer supported