Mauro - You didn't say if the 3590 microcode was also updated, but I'd
        expect it to have been if the Library Manager code also got
an upgrade.  The "BAD MEDIA" indications and tapes ending up ReadOnly
is expected with elder tapes and new 3590 microcode, which has a lower
tolerance for media errors.  The errors are supposedly noted in the
tape header.  If you reclaim the tapes and reset the tape labels, you
may be able to resume using the tapes - but keep an eye on the ones
that were reported.
    Richard Sims, BU