Server hang up when getting the latest definition

I setup SEP11 client on Windows Server 2003 SP2 virtual machine on KVM, and it

sometimes hangs up when getting the latest definition from SEP manager,

When this occurs,it doesnt respond to ping command and I cant connet via RDP. Also, KVM console of this server turns black.

After some minutes, it recovers as if nothing has happened with no error message/event log error.

I've got 15 - 20 guest OSs with the same specs on KVM, but only this virtual machine has this issue.

Has anyone had an issue like this?

Any suggestions would be appreciated.

Thank you.