We currently have a solution developed using SSIS / C#. The SSIS package (amongst other things) has a script task that uses logic developed in the class libraries. This function
I have noticed similar issues with our SSIS/C# mix. We also rely on an external (to SSIS) dll. In our case the DLL had to be copied to the 100/DTS/Binn directory to allow the SSIS package to work from within Visual Studio however when we attempt to run the package using the SQL Package Execution Utility we get an error to the affect that the file could not be found. It does not seem to indicate a version issue so much as a difference in PATH between the Visual Studio and the Package Execution Utility. Even running the package without debug from Visual Studio works. I am going to look into the version issue to see if maybe that is the core complaint on our system but from memory I think it was a file not found type error that affected us. We are using MSSQL 2008 if that makes a difference.