I am having a bit of a linked server problem. 

I created a SQL Server linked server and it's been working fine for last 2 years and suddenly not working. 

**SQL Server** 

> 
> Microsoft SQL Server 2005 - 9.00.5324.00 (X64) Aug 24 2012 18:28:47 
>  Copyright (c) 1988-2005 Microsoft Corporation Enterprise Edition
>  (64-bit) on Windows NT 5.2 (Build 3790: Service Pack 2)
> 
> 
> 

**Oracle client version**

> 
> Oracle - OraClient11g\_home1
> 
> 
> 

**Error 7302:**

> 
> Cannot create an instance of OLE DB provider "OraOLEDB.Oracle" for linked server.
> 
> 
> 

We have enabled Allow in Process in SQL Server for the Oracle Provider.

Has anyone got any ideas on this and what can be done to avoid this happening again?