Error connecting SQL instance

We are getting an error when we try to connect to one of our instances
locally. If we connect to the server remotely, we can manage it with no
problem. However, if we try to manage it from the server itself, we get the
following error:
A connection could not be established to SERVER/INSTANCE
Reason: SQL Server does not exist or access denied.
ConnectionOpen(Connect())..
Please verify SQL Server is running and check your SQL Server registration
properties (by right-clicking on the SERVER/INSTANCE node) and try again.
Our other instance works fine and the instance we are having a problem with
worked fine before, so we don't know what could be causing this. The server
is running Windows Server 2003 Standard.
Are you trying to connect to the local boxes with NT or SQL security?
"DrewB" <DrewB@.discussions.microsoft.com> wrote in message
news:7634F5DF-AB13-4E3C-90D5-E45398E782EE@.microsoft.com...
> We are getting an error when we try to connect to one of our instances
> locally. If we connect to the server remotely, we can manage it with no
> problem. However, if we try to manage it from the server itself, we get
> the
> following error:
> A connection could not be established to SERVER/INSTANCE
> Reason: SQL Server does not exist or access denied.
> ConnectionOpen(Connect())..
> Please verify SQL Server is running and check your SQL Server registration
> properties (by right-clicking on the SERVER/INSTANCE node) and try again.
> Our other instance works fine and the instance we are having a problem
> with
> worked fine before, so we don't know what could be causing this. The
> server
> is running Windows Server 2003 Standard.