[Xperia Arc Android Development] JCDentonMale:
I also lost my root.

Here is the output of the busybox and busybox --list commands typed in terminal:

app_0@android:/ $ /system/xbin/busybox
BusyBox v1.18.5 (2011-07-18 07:43:28 PDT) multi-call binary.
Copyright (C) 1998-2009 Erik Andersen, Rob Landley, Denys Vlasenko
and others. Licensed under GPLv2.
See source distribution for full notice.

Usage: busybox [function] [arguments]...
or: busybox --list[-full]
or: function [arguments]...

BusyBox is a multi-call binary that combines many common Unix
utilities into a single executable. Most people will create a
link to busybox for each function they wish to use and BusyBox
will act like whatever it was invoked as.

Currently defined functions:
[, [[, acpid, add-shell, addgroup, adduser,
adjtimex, ar, arp, arping, ash, awk, base64,
basename, beep, blkid, blockdev, bootchartd,
brctl, bunzip2, bzcat, bzip2, cal, cat,
catv, chat, chattr, chgrp, chmod, chown,
chpasswd, chpst, chroot, chrt, chvt, cksum,
clear, cmp, comm, cp, cpio, crond, crontab,
cryptpw, cttyhack, cut, date, dc, dd,
deallocvt, delgroup, deluser, depmod,
devmem, df, dhcprelay, diff, dirname, dmesg,
dnsd, dnsdomainname, dos2unix, du, dumpkmap,
dumpleases, echo, ed, egrep, eject, env,
envdir, envuidgid, ether-wake, expand, expr,
fakeidentd, false, fbset, fbsplash, fdflush,
fdformat, fdisk, fgconsole, fgrep, find,
findfs, flock, fold, free, freeramdisk,
fsck, fsck.minix, fsync, ftpd, ftpget,
ftpput, fuser, getopt, getty, grep, gunzip,
gzip, halt, hd, hdparm, head, hexdump,
hostid, hostname, httpd, hush, hwclock, id,
ifconfig, ifdown, ifenslave, ifplugd, ifup,
inetd, init, insmod, install, ionice,
iostat, ip, ipaddr, ipcalc, ipcrm, ipcs,
iplink, iproute, iprule, iptunnel, kbd_mode,
kill, killall, killall5, klogd, last,
length, less, linux32, linux64, linuxrc, ln,
loadfont, loadkmap, logger, login, logname,
logread, losetup, lpd, lpq, lpr, ls, lsattr,
lsmod, lspci, lsusb, lzcat, lzma, lzop,
lzopcat, makedevs, makemime, man, md5sum,
mdev, mesg, microcom, mkdir, mkdosfs,
mke2fs, mkfifo, mkfs.ext2, mkfs.minix,
mkfs.vfat, mknod, mkpasswd, mkswap, mktemp,
modinfo, modprobe, more, mount, mountpoint,
mpstat, mt, mv, nameif, nbd-client, nc,
netstat, nice, nmeter, nohup, nslookup,
ntpd, od, openvt, passwd, patch, pgrep,
pidof, ping, ping6, pipe_progress,
pivot_root, pkill, pmap, popmaildir,
poweroff, powertop, printenv, printf, ps,
pscan, pwd, raidautorun, rdate, rdev,
readahead, readlink, readprofile, realpath,
reboot, reformime, remove-shell, renice,
reset, resize, rev, rm, rmdir, rmmod, route,
rpm, rpm2cpio, rtcwake, run-parts, runlevel,
runsv, runsvdir, rx, script, scriptreplay,
sed, sendmail, seq, setarch, setconsole,
setfont, setkeycodes, setlogcons, setsid,
setuidgid, sh, sha1sum, sha256sum,
sha512sum, showkey, slattach, sleep,
smemcap, softlimit, sort, split,
start-stop-daemon, stat, strings, stty, su,
sulogin, sum, sv, svlogd, swapoff, swapon,
switch_root, sync, sysctl, syslogd, tac,
tail, tar, tcpsvd, tee, telnet, telnetd,
test, tftp, tftpd, time, timeout, top,
touch, tr, traceroute, traceroute6, true,
tty, ttysize, tunctl, udhcpc, udhcpd,
udpsvd, umount, uname, uncompress, unexpand,
uniq, unix2dos, unlzma, unlzop, unxz, unzip,
uptime, usleep, uudecode, uuencode, vconfig,
vi, vlock, volname, wall, watch, watchdog,
wc, wget, which, who, whoami, xargs, xz,
xzcat, yes, zcat, zcip

app_0@android:/ $ /system/xbin/busybox --list
[
[[
acpid
add-shell
addgroup
adduser
adjtimex
ar
arp
arping
ash
awk
base64
basename
beep
blkid
blockdev
bootchartd
brctl
bunzip2
bzcat
bzip2
cal
cat
catv
chat
chattr
chgrp
chmod
chown
chpasswd
chpst
chroot
chrt
chvt
cksum
clear
cmp
comm
cp
cpio
crond
crontab
cryptpw
cttyhack
cut
date
dc
dd
deallocvt
delgroup
deluser
depmod
devmem
df
dhcprelay
diff
dirname
dmesg
dnsd
dnsdomainname
dos2unix
du
dumpkmap
dumpleases
echo
ed
egrep
eject
env
envdir
envuidgid
ether-wake
expand
expr
fakeidentd
false
fbset
fbsplash
fdflush
fdformat
fdisk
fgconsole
fgrep
find
findfs
flock
fold
free
freeramdisk
fsck
fsck.minix
fsync
ftpd
ftpget
ftpput
fuser
getopt
getty
grep
gunzip
gzip
halt
hd
hdparm
head
hexdump
hostid
hostname
httpd
hush
hwclock
id
ifconfig
ifdown
ifenslave
ifplugd
ifup
inetd
init
insmod
install
ionice
iostat
ip
ipaddr
ipcalc
ipcrm
ipcs
iplink
iproute
iprule
iptunnel
kbd_mode
kill
killall
killall5
klogd
last
length
less
linux32
linux64
linuxrc
ln
loadfont
loadkmap
logger
login
logname
logread
losetup
lpd
lpq
lpr
ls
lsattr
lsmod
lspci
lsusb
lzcat
lzma
lzop
lzopcat
makedevs
makemime
man
md5sum
mdev
mesg
microcom
mkdir
mkdosfs
mke2fs
mkfifo
mkfs.ext2
mkfs.minix
mkfs.vfat
mknod
mkpasswd
mkswap
mktemp
modinfo
modprobe
more
mount
mountpoint
mpstat
mt
mv
nameif
nbd-client
nc
netstat
nice
nmeter
nohup
nslookup
ntpd
od
openvt
passwd
patch
pgrep
pidof
ping
ping6
pipe_progress
pivot_root
pkill
pmap
popmaildir
poweroff
powertop
printenv
printf
ps
pscan
pwd
raidautorun
rdate
rdev
readahead
readlink
readprofile
realpath
reboot
reformime
remove-shell
renice
reset
resize
rev
rm
rmdir
rmmod
route
rpm
rpm2cpio
rtcwake
run-parts
runlevel
runsv
runsvdir
rx
script
scriptreplay
sed
sendmail
seq
setarch
setconsole
setfont
setkeycodes
setlogcons
setsid
setuidgid
sh
sha1sum
sha256sum
sha512sum
showkey
slattach
sleep
smemcap
softlimit
sort
split
start-stop-daemon
stat
strings
stty
su
sulogin
sum
sv
svlogd
swapoff
swapon
switch_root
sync
sysctl
syslogd
tac
tail
tar
tcpsvd
tee
telnet
telnetd
test
tftp
tftpd
time
timeout
top
touch
tr
traceroute
traceroute6
true
tty
ttysize
tunctl
udhcpc
udhcpd
udpsvd
umount
uname
uncompress
unexpand
uniq
unix2dos
unlzma
unlzop
unxz
unzip
uptime
usleep
uudecode
uuencode
vconfig
vi
vlock
volname
wall
watch
watchdog
wc
wget
which
who
whoami
xargs
xz
xzcat
yes
zcat
zcip
app_0@android:/ $

Interestingly, here is the output of the su command :

app_0@android: / $ su
su: unknown user root
1|app_0@android: / $