An operations error occurred,Microsoft.ActiveDirectory.Management.Commands.GetADGroupMember

I finally have some 2008 r2 servers that I get to use the Active Directory module cmdlets on.  Strange thing though,  when I run Get-ADGroupMember on the Administrator group, I get this error:

An operations error occurred,Microsoft.ActiveDirectory.Management.Commands.GetADGroupMember

I see a few other people say they have experienced this online, but no one gets to why.  Most of the time, the people responding try it and they don't have a problem.  It works fine with any other group, it just fails with the Administrator group. 

I can get what I need like this:

([ADSI]'LDAP://CN=Administrators,CN=Builtin,DC=Domain,DC=COM').member

but that doesn't really answer my question about what the problem is.