Sudo unable to open /etc/sudoers

Question

Whenever I try to do anything at all with sudo on my fresh x86-64 Arch install, it prints out this error:
sudo: unable to open /etc/sudoers: Permission denied
sudo: no valid sudoers sources found, quitting
sudo: unable to initialize policy plugin
This is on a fresh Arch install from the core Image CD, packages initially installed from the CD and then upgraded with #pacman -Syu. I can edit sudoers just fine with visudo, and installing outdated versions of sudo produce the same error. File permissions on both /usr/bin/sudo and /etc/sudoers both look as they should be. Also, users and user groups don't seem to be an issue.
Found this related StackExchange thread and here are the outputs of strace and ltrace if anyone can interpret them: http://unix.stackexchange.com/questions … most-files
Ltrace:
# ltrace -u notthemessiah sudo true 2>&1 | egrep '(sudo|stat|set.*[ug].*id)'
bindtextdomain("sudo", "/usr/share/locale") = "/usr/share/locale"
textdomain("sudo") = "sudo"
strlen("sudo") = 4
memcpy(0x01c6f299, "sudo", 4) = 0x01c6f299
fopen("/etc/sudo.conf", "r") = 0
__xstat(1, "/usr/lib/sudoers.so", 0x7fff6b0913d0) = 0
dlopen("/usr/lib/sudoers.so", 257) = 0x01c6f630
dlsym(0x01c6f630, "sudoers_policy") = 0x7f33e2f96960
__xstat(1, "/usr/lib/sudoers.so", 0x7fff6b0913d0) = 0
dlopen("/usr/lib/sudoers.so", 257) = 0x01c6f630
dlsym(0x01c6f630, "sudoers_io") = 0x7f33e2f969c0
fputs("sudo", 0x7f33e35296e0sudo) = 1
fputs("unable to open /etc/sudoers", 0x7f33e35296e0unable to open /etc/sudoers) = 1
fputs("sudo", 0x7f33e35296e0sudo) = 1
fputs("no valid sudoers sources found, "..., 0x7f33e35296e0no valid sudoers sources found, quitting) = 1
fputs("sudo", 0x7f33e35296e0sudo) = 1
+++ exited (status 1) +++
Strace:
# strace -u notthemessiah sudo true 2>&1 | egrep '(sudo|set.*[ug].*id)'
execve("/usr/bin/sudo", ["sudo", "true"], [/* 22 vars */]) = 0
open("/etc/sudo.conf", O_RDONLY) = -1 ENOENT (No such file or directory)
stat("/usr/lib/sudoers.so", {st_mode=S_IFREG|0755, st_size=185352, ...}) = 0
open("/usr/lib/sudoers.so", O_RDONLY) = 3
stat("/usr/lib/sudoers.so", {st_mode=S_IFREG|0755, st_size=185352, ...}) = 0
open("/usr/share/locale/en_US.UTF-8/LC_MESSAGES/sudoers.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale/en_US.utf8/LC_MESSAGES/sudoers.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale/en_US/LC_MESSAGES/sudoers.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale/en.UTF-8/LC_MESSAGES/sudoers.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale/en.utf8/LC_MESSAGES/sudoers.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale/en/LC_MESSAGES/sudoers.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
lstat("/etc/sudoers", {st_mode=S_IFREG|0440, st_size=2849, ...}) = 0
setresgid(4294967295, 0, 4294967295) = 0
setresuid(0, 1, 4294967295) = 0
open("/etc/sudoers", O_RDONLY) = -1 EACCES (Permission denied)
setresuid(4294967295, 0, 4294967295) = 0
write(2, "sudo", 4sudo) = 4
write(2, "unable to open /etc/sudoers", 27unable to open /etc/sudoers) = 27
setresuid(4294967295, 1, 4294967295) = 0
setresgid(4294967295, 0, 4294967295) = 0
setresuid(4294967295, 0, 4294967295) = 0
setresuid(1000, 0, 4294967295) = 0
setresgid(1000, 1000, 1000) = 0
write(2, "sudo", 4sudo) = 4
write(2, "no valid sudoers sources found, "..., 40no valid sudoers sources found, quitting) = 40
open("/usr/share/locale/en_US.UTF-8/LC_MESSAGES/sudo.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale/en_US.utf8/LC_MESSAGES/sudo.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale/en_US/LC_MESSAGES/sudo.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale/en.UTF-8/LC_MESSAGES/sudo.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale/en.utf8/LC_MESSAGES/sudo.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale/en/LC_MESSAGES/sudo.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
write(2, "sudo", 4sudo) = 4

Answer 1

No, I used visudoers and everything relating to that correctly. It's just probably something that happened while installing the core packages from the install CD that caused problems. As of now, I just reinstalled Arch on a new partition (this was a fairly fresh install) and it seems to work just fine. I was willing to continue to test the issue, but resizing the partition seems to have corrupted it somehow.