Thanks nrxnrx very much!
Following your advice, I have solved the problem in the following way:
1) First, I noticed that every time I put the stick with the firmware .GEL, it seemed that the firmware update process always started ok but (perhaps because I had previously used the bootloader .GEL twice) it invariable ended stuck with the first light blinking (Ramp). I was always using an old brandless 64MB drive.
2) I full formatted another stick drive, a 2GB Kingstone DataTraveller II. Then I copied the firmware .GEL file.
3) Surprisingly, this thumb drive was not recognized by the instrument as it only lit up Mod, Utility and Store buttons. This is just what describes Rigol in its DG4000 Firmware Upgrade Procedure. pdf file. Notice that this drive was and is recognized under the Store menu by the DG4K.
4) I full formatted my original 64MB thumb drive and copied the .GEL file again.
5) Yet more surprisingly, the update process then advanced further the Ramp button and ended successfully!
6) I suspect that having used the "incompatible" thumb drive may reset the previously perturbed update sequence and allowed me to start a fresh new one
.
Now I have the instrument working, upgraded to version 01.12 and keeping the DG4162 model!!
I hope my painful experience can help someone in the future.
I have one last question: Now with firmware 01.12, would I be able to do the factory reset calibration to get a flat output beyond 60MHz (the bandwidth of my original DG4062)?
Many thanks,
Andrés