After installing SP2 on SQL Server 2005 x64, when trying to open existing SSIS package or try to add data component to a new SSIS package, is giving error saying that designer could not be initialised.: "After installing SP2 on SQL Server 2005 x64, when trying to open an existing SSIS package or trying to add data component to a new SSIS package, you may receive an error saying that the designer could not be initialised.

This problem occurs because the installer unregisters the 32-bit Dts.dll file when the installer installs the 64-bit Dts.dll file. The 64-bit Dts.dll file is installed together with SQL Server 2005 SP2. Additionally, the 64-bit Dts.dll file may be installed together with any SSIS hotfix package that contains the 64-bit Dts.dll file.

Solution 1: Un-install SQL Server 2005 client tools and reinstall it again.

Solution 2: Register dts.dll
%windir%\syswow64\regsvr32 '%ProgramFiles(x86)%\Microsoft SQL Server\90\dts\binn\dts.dll' [Read Full Article]"

(Via Latest SQL-Server-Performance.com Articles/Tips/FAQ's and Reviews.)