SBS 2003 to SBS 2011 post migration issues

We've had a few recent events (in the last 2 months) where our SBS 2011 server (Hyper-V VM) has been completely inaccessible on the network in all ways except for direct console access. In order to restore accessibility on the network we've had to reboot the VM. After the reboot all is well.

The SBS 2011 server has been in production since last November, but the problem just started back in February and it's happened 3 times since. I cannot relate any particular event as the source of the issue, so I'm just going through the event logs and addressing any issue that seems relevant.

I'm unable to figure out how to resolve the below issue which appears to be (obviously) role assignment related. It just so happens that it's actually referencing the machine name of the SBS 2011 server and not a particular user object.

"(Process w3wp.exe, PID XXXX) "RBAC authorization returns Access Denied for user privatedomain.local/Domain Controllers/SBS2011. Reason. No role assignments associated with the specified user were foundo n Domain Controller SBS2011.privatedomain.local"

What do you think?

MO