When importing files using XMLports, and especially when handling text files, file encoding is important. If the XMLport expects ASCII, and you feed it UTF-8, you may get scrambled data. If you have mismatching unicode input files, it may just fail altogether. Therefore, making sure that encoding is correct before you actually start gobbling input files might be important.
At least it was for me. I am currently automating data migration for a major go-live, and I am feeding some 30 input files to NAV, and I want to make sure they are all encoded correctly before I enter a process which would take another geological era to complete.