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 18.104.22.168
ns1 : http(s), ftp(s), DNS Master, ISPConfig
sql : MySQL database users
mail : All mail system
ns2 : DNS Slave