This has been happening to me A LOT now that I seem to have my USB storage hooked up.
When switching menu's it freezes. Sort of. Like right now, it's playing that "wait a sec... loading..." music and it says "Wii U Menu" on my screen, but it's just not loading that menu. It locks here and I can't even shut it down, I have to pull the plug out of the console.
Anyone else have this problem? Is it even related to my USB device or is it just coincidence?