The joy that is SP2 just keeps on giving. Microsoft released a hotfix (KB934458) to bring it up to 3054:
FIX: The Check Database Integrity task and the Execute T-SQL Statement task in a maintenance plan may lose database context in certain circumstances in SQL Server 2005 builds 3042 through 3053
This came down through Windows automatic updates. It was an 18MB package and took roughly 11 minutes on my laptop.
There is also a fix (KB934459) in case you're running a higher build of SQL Server 2005 (3150 - 3158). I'm not sure exactly how these apply or why there are two ranges of build numbers.