kblankscrn.kss: 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/kblankscrn.kss - from package: kdebase-workspace

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

On Debian possible default full paths are:

/usr/bin/kblankscrn.kss - from package: kde-workspace-bin

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

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