The Managed Metadata Service or Connection is currently not available.

I've been trying to create new Managed Metadata services but get this error when trying to manage them:
The Managed Metadata Service or Connection is currently not available. The Application Pool or Managed Metadata Web Service may not have been started. Please Contact your Administrator.

I've checked that the application pool that the Metadata service uses is running and that the account it's running under is in the farm administrators group. I've checked that the WCF hotfix is applied on the system by re-downloading KB971831 (I have Windows 2K8 SP2) and trying to run it again but it says it doesn't apply to my system (as I had installed it before installing SharePOint)

I'm not sure what else to do - can anyone give any pointers?

Thanks