samba - Nov 2005 - Access denied when creating a new local group

Hi,

If I run this: (where LOCALHOST is the local server name)

 $ net rpc group add test -U LOCALHOST\\root

Then providing I've put in the correct password, I get this:

 add group failed: NT_STATUS_ACCESS_DENIED

I'm using "security = domain", so is there some reason why local
groups
are not allowed in this configuration?  I've tried other accounts, but
whether they're mapped to the root user in username.map or not, I still
get the access denied error.

What is the correct way to create a local group when using
"security = domain"?

Thanks,
Adam.