Clients reboot before Starting the Deployment

Hello,

I have the following problem. I use multicast to provide my Image over the network. I tried to deploy my Image to 5 clients via multicast. The Deploy server waits for 5 clients. And when all clients are ready to deploy, 4 of the 5 clients are rebooting. Only one client (random) is deploying. Why? In the Management console I see the error attached by my screenshot.

I hope somebody could help me.

regards,
Sven