- It is normal the camera do BEEP and the led turns between orange and green quickly while updating?
?? (you can see the youtube video)..... someone did notice upgrading taking more than one minute in any case?
No, there should be no beeps & no disco lights, duration should be < 20 seconds.
(I haven't updated a A620 yet, but i had no problems with updating an Ixus 50 some time ago)
- I checked the md5sum of the two firmware files, the one extracted of the zip file, and the one copied and into the SD........... do you think maybe the problem could be the SD card?
?
- Is there maybe any other parameter of my spanish A620 which could cause upgrading fails?
?
Maybe, but rather unusual.
Some suggestions - but beware: it's your camera

- use a small, reliable SD card - e.g. the small 16 or 32MB card delivered with your camera
- reset your camera to the default settings (from the Canon menu)
- format the card in the camera (full format mode)
- use a reliable card reader, always eject the card/reader with the corresponding OS function ("remove hardware" under Windows)
- charge the batterie before updating
- clean the batterie contacts
- while updating: do not touch buttons or move the camera
Maybe removing the small backup batterie (a small coin cell, used to backup the cameras date & time / settings) for some hours & setting up date & time after re-insert the batterie could be helpful...
You can also try to update the firmware via USB with the original firmware loader...