VM after reboot un-reacheble and un-pingeble

Hi,

We have an strange problem. We have an several VM's. When the VM's start the VM are pingeble and can users login. But when the reboot the machines the users cannot login anymore and they aint pingeble anymore. When the network is disable/ enabled witin the VM it is funtioning again. Same effect when the nic is deactivate/ activate  in the manager.

First we thouth that the DHCP server was the problem. And looked at the DHCP server but our 200 fat clients do not have this problems. We have installed an machine with an fixed IP address the same thing happens.

When the VM is shutdown and startup again the vm is reacheble