If you have installed Visual Studio 2005 alongwith 2008 version and are working on SSIS Script Components or Script Tasks, then you will find that clicking on Design Script button on the component will give an error "Cannot show visual studio for application editor".
The solution is this is to either remove Visual Studio 2008 or install SQL Server 2005 SP3 edition. In my personal laptop, I did both as I didn't need Visual Studio 2008. But in case, you need both IDEs, you can install SP3 and fix the issue for good. It worked for me.