That's not what I asked. You said you were having problems changing the data type. I'm asking you where you are trying to change the data type that you're getting this problem.

Usually, the change should be made in the Connection Manager first. Then the object(s) in the Data Flow task have to be refreshed (open, then click on Column Mappings, then close the Transformation) to "take" the metadata changes. That clears up any warnings or errors. This may need to be done for multiple objects, depending on if you're changing the source or the destination data.