[estecb]

Finally, I fixed it!
It turns out, it had some bad sectors in the MBR (not really, somewhere near it... the first 26MB are reserved and that's where the bad sectors were found). After backing up the MBR, all the other partitions, "zeroing" the MBR, restore the MBR and the partitions, it worked like a charm.

Here are the steps I followed, I did it on my Ubuntu machine (there is no way you can do all this on Windows):
1_ Use rupor-rescue.7z (the MENU + HOME method) to enter the recovery mode.
2_ Connect the device to your PC. You should see all the device's partitions.
3_ Open a Terminal, run "sudo badblocks -v /dev/sdb"
(/dev/sdb being the sony device path, run "df" to check yours or use the Ubuntu "disk utility")
4_ badblocks should report some bad sectors (whitin the first 10% or so), otherwise don't continue this guide.
5_ Backup, run "sudo dd if=/dev/sdb of=/home/user/sdb.img iflag=direct conv=noerror,sync"
(/home/user beign the path to save the disk image)
This command clones the device by recovering good sectors and writting zeroes on the bad ones.
If this takes way too long (more than 1 hour), you may try removing the "iflag=direct".
A "Input/output error" may appear, that's normal.
6_ Check your output file ("/home/user/sdb.img") is about 2GB.
7_ Restore, "sudo dd if=/home/user/sdb.img of=/dev/sdb"
8_ Run "sudo badblocks -v /dev/sdb" again, it should report 0 bad sectors.
8b_ If it reports bad sectors, try formatting and then restoring again. Format, run "sudo dd if=/dev/zeros of=/dev/sdb" and then repeat the step 7 (restore).
9_ That's it, safe extract your USB, reset the device, turn it on and it should work!

Actually, I cheated... I did not have to backup the MBR and all the partitions, since I got another PRS-T1 I backed up the working one and then restore it in the old broken one. I had to format before restore (step 8b).

Happy holidays and new year!