On Monday, the SQL Server Release Services team released cumulative updates for both SQL Server 2008 SP1 and SQL Server 2008 SP2. The cumulative update for SP2 restores the fixes that were potentially undone by applying SP2 (or the SP2 CTP) after applying CU9 or CU10 to SP1. Confusing, yes, but at least it's straightened out now. We won't have to deal with this until the next service pack.
- SQL Server 2008 SP1 Cumulative Update #11- build # 10.0.2804
- SQL Server 2008 SP2 Cumulative Update #1 – build # 10.0.4266
And no, neither of these updates are applicable to SQL Server 2008 R2.