dasilvarsa
To be absolutely correct, GarminCure3 is not designed for users who can't enter the real pre-boot mode. dnx9260bt's firmware is not very different from a regular nuvi firmware, it's a regular GarminOS-based firmware, nothing magical.

To prevent such accidents, I'm going implement a pre-boot mode checker in GarminCure3, which would send a few USB commands and decide if it's communicating with fw_all.bin (pseudo pre-boot mode) or bootloader (real pre-boot mode), and then disallow/allow running updater.exe.
Well, also I will probably make GarminCure3 remove all firmware regions except boot.bin, fw_all.bin, fw_all1.bin to prevent those "unable to program the requested memory region" messages.

mylona79
Try doing the following:
1) Turn off the device
2) Connect the device to the PC and run updater.exe with appropriate firmware (you can use GarminCure3 with ORIGINAL option).
3) Start pressing [SRC] and [ATT] keys. Press and release [Reset] key to start the device. Continue pressing [SRC] and [ATT] until your device is detected by updater.exe.

If this doesn't help, Alexander claims that it's possible to enter pre-boot mode by connecting two pins on the PCB. I will upload the photo of the PCB later.