Some Gentoo users are encountering problems because
USB_EHCI_TT_NEWSCHED isn't set in the defconfig (and Gentoo
differs from other distros in not providing a distro .config).
Alan Stern has said there's no reason to not set it, and the
ability to turn it off at all should probably be yanked:
(The problem also theoretically affects the sh, arm, mips,
powerpc, and sparc archs, but those would be other patches if
this one that fixes 98% of the problem is accepted).