Error connecting to a SQL server 2008R2 instance via SSMS

I get a "cannot generate sspi context" when trying to connect to a SQL 2008R2 instance.

There are not duplicate SPN records on the network, I've checked this.

We are getting this error on the SQLservice account:

The application-specific permission settings do not grant Local Activation permission for the COM Server application with CLSID
to the user Domainname\SQL_service SID (S-1-5-21-1728536662-146330824-3268609631-1851) from address LocalHost (Using LRPC) running in the application container Unavailable SID (Unavailable). This security permission can be modified using the Component Services administrative tool.

But this is pretty much all I can see from an Event Log POV

I can log-in locally used my UN adn PW as authentication but not remotely from my PC.
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Dave BaldwinFixer of ProblemsCommented:
Maybe Remote Connections are not enabled for that database engine.  On that machine, run SMSS.  Right click on the server line and click on Properties and then Connections.  Near the bottom of the window, make sure the checkbox before "Allow remote connections to this server" is checked.

You may also have to make sure that both machines have the same protocols enabled for the server and the SQL Native Client.
wannabecraigAuthor Commented:
Hi, do you mean SSMS?

We used to be able to connect to this machine remotely, then it just stopped.  Not idea why.

Which same protocols?

I'm not sure what a SQL native client is either, sorry, can you explain?
Dave BaldwinFixer of ProblemsCommented:
#Hi, do you mean SSMS?

#We used to be able to connect to this machine remotely, then it just stopped.  Not idea why.

Something changed and you need to find out what that is.

#Which same protocols?
SQL Connection protocols
#I'm not sure what a SQL native client is either, sorry, can you explain?
SQL Native Client is the driver that connects the client to the server.  It is installed with the server and must be installed on machines without the server if they are to connect to the server.
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Mark GalvinManaging Director / Principal ConsultantCommented:
wannabecraigAuthor Commented:
Article says it ojnly applied to the following:

Microsoft SQL Server 2000 Standard Edition
Microsoft SQL Server 7.0 Standard Edition
Microsoft SQL Server 2005 Standard Edition
Microsoft SQL Server 2005 Developer Edition
Microsoft SQL Server 2005 Enterprise Edition
Microsoft SQL Server 2005 Express Edition
Microsoft SQL Server 2005 Workgroup Edition
Keywords: kbinfo KB269541

It's worth noting that we were able to connect  to this server at one point.
wannabecraigAuthor Commented:
I found out the issue here.  For some reason, the 'SQL server' service was set to use the
NT Service account MSSQLSERVER.  I'm not sure why or how this was switched.
Are there any installs/configs that would cause this>?

I changed this to use the Domain service account and the issue was resolved.

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Microsoft SQL Server 2008

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