Unable to use sudo on fresh kubuntu 7.10 install

I've just done an install of Kubuntu 7.10 using the Alternative install CD (I am using root on RAID1+LVM2) sudo is non-functional

r@windy:~$ sudo cat /etc/shadow
[sudo] password for r:
r@windy:~$
r@windy:~$ sudo cat /etc/shadow
r@windy:~$ strace -ff sudo cat /etc/shadow
execve("/usr/bin/sudo", ["sudo", "cat", "/etc/shadow"], [/* 32 vars */]) = 0
brk(0) = 0x8062000
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7fde000
access("/etc/ld.so.preload", R_OK) = -1 ENOENT (No such file or directory)
open("/etc/ld.so.cache", O_RDONLY) = 3
fstat64(3, {st_mode=S_IFREG|0644, st_size=50270, ...}) = 0
mmap2(NULL, 50270, PROT_READ, MAP_PRIVATE, 3, 0) = 0xb7fd1000
close(3) = 0
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
open("/lib/libpam.so.0", O_RDONLY) = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0\3\0\1\0\0\0000\32\0"..., 512) = 512
fstat64(3, {st_mode=S_IFREG|0644, st_size=37880, ...}) = 0
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7fd0000
mmap2(NULL, 40660, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xb7fc6000
mmap2(0xb7fcf000, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x8) = 0xb7fcf000
close(3) = 0
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
open("/lib/tls/i686/cmov/libdl.so.2", O_RDONLY) = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0\3\0\1\0\0\0p\n\0\000"..., 512) = 512
fstat64(3, {st_mode=S_IFREG|0644, st_size=9684, ...}) = 0
mmap2(NULL, 12412, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xb7fc2000
mmap2(0xb7fc4000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1) = 0xb7fc4000
close(3) = 0
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
open("/lib/tls/i686/cmov/libc.so.6", O_RDONLY) = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0\3\0\1\0\0\0\260a\1"..., 512) = 512
fstat64(3, {st_mode=S_IFREG|0644, st_size=1339816, ...}) = 0
mmap2(NULL, 1349136, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xb7e78000
mmap2(0xb7fbc000, 12288, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x143) = 0xb7fbc000
mmap2(0xb7fbf000, 9744, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0xb7fbf000
close(3) = 0
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7e77000
set_thread_area({entry_number:-1 -> 6, base_addr:0xb7e776b0, limit:1048575, seg_32bit:1, contents:0, read_exec_only:0, limit_in_pages:1, seg_not_present:0, useable:1}) = 0
mprotect(0xb7fbc000, 4096, PROT_READ) = 0
munmap(0xb7fd1000, 50270) = 0
geteuid32() = 1000
write(2, "sudo: ", 6sudo: ) = 6
write(2, "must be setuid root", 19must be setuid root) = 19
write(2, "\n", 1
) = 1
exit_group(1) = ?
Process 10342 detached
r@windy:~$ ls -al `which sudo`
-rwsr-xr-x 2 root root 91776 2007-06-15 05:49 /usr/bin/sudo

Ideas?