userhelper: 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/sbin/userhelper - from package: usermode

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

On Debian possible default full paths are:

/usr/sbin/userhelper - from package: usermode

You may install the required package with command apt-get install {package}

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