access denied with "enable-psremoting" on a local DC 2008 R2 by Thierry_B

I'm trying to install SCVMM but it fails. After a few search, I found out that the command:
enable-psremoting using a PS console returns me:
Set-WSManQuickConfig: Access is denied

I'm connected using the domain admin account (administrator) with a password.
The WinRM service is running under the "network" account.
In the registry, the value of LocalAccountTokenFilterPolicy is set to 1.
I changed the security settings in WMI properties.

Thanks for any ideas you could have,
Thierry