There is an issue with the SQL Server Database engine components of original Cumulative Update 6 package (CU6). Microsoft release a fix to all servers with CU6 installed, in order to repair the error. (Index corruption ocurred).
There is a COD (Critical on-demand) for installed CU6
Microsoft removes CU6 link and creates a new Cumulative Update, CU7
Cumulative Update 7 (SQL Server 2008 R2 SP2)