I managed to find another DSi and after some improvising, I finally applied the 1.4.2 update. The improvising I am referring to is the fact that I had install the old Acekard2i 4.23 firmware (in ak2_423_20100721_release.zip) to run the 1.4.2 update, and then remove the 4.23 stuff before adding AKAIO 1.8.7.