avg_checkvsync: 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/avg_checkvsync - from package: python-libavg

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

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