Yes, it's multiserver system. But it worked fine during 1 month and since 1 week, it bug
There are no package updated before the problem.
4 virtual machines with Debian Lenny updated on proxmox (openvz) with ISPConfig 220.127.116.11
ns1 : http(s), ftp(s), DNS Master, ISPConfig
sql : MySQL database users
mail : All mail system
ns2 : DNS Slave