If you have already installed SQL Server 2005 Service Pack 2 it is recommended that you apply the Critical Update referenced in KB933508 http://support.microsoft.com/kb/933508.
There is an issue in SP2 that causes maintenance plan cleanup tasks to remove data before the specified cleanup interval. The Critical Update to resolve this issue can be downloaded from http://www.microsoft.com/downloads/details.aspx?familyid=e2c358a1-ecc4-4c49-8f65-daa6b7800eec&displaylang=en.
