I suspect filesystem corruption here. As this is likely to be your root filesystem you won't be able to do a full
fsck while the system is live, so do
sudo shutdown -r -F now which should shutdown and reboot (the
-r) forcing a run of
-F) as the system comes back up (at a point where issues found can be more safely fixed). You might want to update your backups first, if only for the sake of paranoia (in case something is seriously wrong and the machine won't reboot cleanly).
It could also be a file locking issue, though I would expect a different error message in that case. To see what processes are actively usng those files you can run
lsof | grep locale.