If you load an existing DTV Import scenario, and change the input file, and then attempt to Save the Scenario, and get an error message Reqeust Processing Failed, or Something Unexpected Happened.
There are two was to workaround this. You can either
1. Use Scenario Save As to save any changes. However, this option will lose the label names on all your Matching Steps.
2. To avoid losing your matching step names, make sure you know the location of your original scenario import file, then make changes to the input file, mappings, connditions, and mapping steps as needed. When your done with modifications, back to the step 1, and change the import file back to the original file and then click Save Scenario. Doing this will prevent the matching step names from being lost.