If you updated to 4.0 via Waninkoko's updater, your IOSes are still fine, and you can use the old 3.2 version of the dvdx installer with advanced options... therefore you can install to IOS202 for use with MPlayer-CE with USB2.0 support. I believe you can also use the old version of the dvdx installer if you've updated to 4.0 via Nintendo, but then downgraded your IOSes afterward. I don't know whether the 3.4 version of dvdx works if you have updated IOSes via Nintendo update. Keep in mind though, that even if it does, there are no advanced install options, meaning no USB2.0 support for Mplayer-CE.
Fuck those things, six self.checkouts in parallel are slower than one manned register, and they have to have someone stand next to them to help people and validate age if you're buying beer, and unlock the machine when it gets into the MYSTERY OBJECT IN THE BAGGING AREA OH GOD HELP, HELP, CALL FOR HELP mode.