lxpanel: 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 Debian possible default full paths are:

/usr/bin/lxpanel - from package: lxpanel

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

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