I executed dd if=/dev/zero of=/dev/block/mmcblk1p1
I've read in droid-developers.org that mbmloader is locked so I thought dd was going to give me write errors. I was wrong, and dd wrote zeros in the mbmloader partition. Now, phone is completely dead and I'll have to get a new one.
But I think that if it's possible to change mbmloader code with zeros, why can't we replace it with a new unsigned bootloader using dd? I couldn't find many real explanations why bootloader can't be replaced besides "it's locked and forget about it", so dd may be a way to replace it. We gonna need the opinion of someone with more knowledge about low-level programming and Defy's hardware.
Bye... And never type this in your Defy if you like it.