Backup Client loses Trust After Restore

I have installed Backup Exec 2012 SP2. I have the V-Ray Licenses to backup our Hyper-V hosts. Backup. Backup Jobs run successfully, but when I do a system state restore of a VM, the trust to the Domain Controller is lost. I have to disjoin the VM from the domain and rejoined it again, and then the trust relationship is restored. I understand that this can happen with old Backup Media, but the time difference of the Backup and the running environment is less than 3hours.

Does anyone have any hints?

Thanks!

James