[arch-general] Keyboard and mouse not working in X

Last night, I updated my system with everything from the past week or so. Everything went smoothly. Today, however, I discovered that upon launching X, using, for instance,

xinit /usr/bin/xterm my computer stops responding to my USB keyboard and mouse. I can't even switch back to the console using CTRL-ALT-FN. If I SIGTERM the process from ssh, X closes normally and my keyboard resumes function in the console. I've checked, and none of the files in /etc/X11 were modified anytime recently.

Any advice? pants.