But I don´t know what´s the problem !!!
The problem is originated when I transfer files between my PC and the Amiga using Aexplorer.
After re-formatting the disk, I restored all the original disk files from a backed-up version stored in my PC hard disk, I don´t know what´s the problem but it looks like the Aexplorer changes something in the file when translates the files from the Amiga to the PC when I backed up in the first time.
Also UAE gives me these error messages when I tried to "boot" from these files.
I fixed up copying a WB13.ADF directly to DF0: and then I copied the system files from the diskette to hard disk.
STRANGE, UH??
Well it's not strange. You said it yourself: "looks like the Aexplorer changes something in the file", that is: Amiga Explorer loses the P bit.