Group Policy Modelling Fails when using certain DCs

Hi,

We have five DCs in our domain and were doing some routine modelling when we tried to model a policy with one DC. We found that this failed (In the summary we find that component status in user and computer has a red cross against it) with the error 

We've checked in the event log and can see a couple of Userenv errors (1030 and 1080). I've tried the usual DCDiag, checking DNS etc and everything seems fine. The weird bit for me is that if we try and model the same thing but choose a different DC it works fine. 

From testing we seem to have 2 DCs that can model fine and 3 that can't.

Any ideas guys?

Thanks,

Stephen