SQL Server Management Studio (SSMS) - Method not found unable to connect.

Hello, 

We have started in place upgrade for SQL Server 2008 Ent edition to SQL Server 2008 R2 ENT.  

It failed to upgrade. and residing SQL 2008 instance did not come up. 

As a fallback plan, we installed fresh SQL 2008 and restored system back. 

Now connect new instance of 2008 , using SSMS we are not able to get in the server. we have following error msg. 

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TITLE: Connect to Server
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Cannot connect to LONSTUBQANAD\MSSQLQA.

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ADDITIONAL INFORMATION:

Method not found: 'Microsoft.SqlServer.Management.Common.DatabaseEngineType Microsoft.SqlServer.Management.Common.ConnectionManager.get_DatabaseEngineType()'. (Microsoft.SqlServer.Management.SqlStudio.Explorer)

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BUTTONS:

OK
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Your help will save a lot rework for us.

Thanks in Advance. 

Sid.