xpbsmon: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/xpbsmon - from package: torque-gui

You may install the required package with command yum install {package}

Error in other languages:
xpbsmon: bevel nie gevind nie
xpbsmon: comandă negăsită
xpbsmon: comando não encontrado
xpbsmon: commande introuvable
xpbsmon: command not found
xpbsmon: käsku ei ole
xpbsmon: không tìm thấy lệnh
xpbsmon: komanda nerasta
xpbsmon: Kommando nicht gefunden.
xpbsmon: kommandot finns inte
xpbsmon: komut yok
xpbsmon: nie znaleziono polecenia
xpbsmon: níor aimsíodh an t-ordú
xpbsmon: no se encontró la orden
xpbsmon: no s'ha trobat l'ordre
xpbsmon: opdracht niet gevonden
xpbsmon: parancs nem található
xpbsmon: perintah tidak ditemukan
xpbsmon: príkaz nenájdený
xpbsmon: příkaz nenalezen
xpbsmon: команда не найдена
xpbsmon: командата не е открита
xpbsmon: 命令找不到
xpbsmon: コマンドが見つかりません