Hi Cenicero, the only option for you is to send it back.
I am in the same boat, I tried to the update function using the SIGNTEK software. The same thing happened to me. For me, initially the screen got stuck on this line: "it is bootloading... please wait". From there on, if I tried updating anything else, SIGNTEK would tell me that that it could not update because the controller was running.
Then the manufacturer suggested I could press the "OK" button before plugging the DSP Handle into the computer and this would give me the option to reset the program. This got me to the Emergency screen,where I could format the drive, but it had no effect on repairing the firmware.
I was then informed that there are two editions for the DSP. If you started the DSP originally and it had "CNC ROUTER" as the initial logo, then this one needs to be sent back to China for repair, there is no way to do it through the SIGNTEK software.
Let this be a warning to anyone with the DSP controller. Don't mess with it, you will regret it if you do. I don't know why they have designed the DSP to make it so simple to stuff up the Firmware, but there you go..