What kind of delimiter are you using? Can the data have that character in it. Had this type of problem using CSV and single quotes. Name field had a quote in the last name. Messed stuff all up until I found it.
My problem is that am getting the wrong data in the worng colums after the import. See example for my date column am getting numbers but am doing the mapping correct i feel its the file, this is only a recent problem as it was working before ok. Extract file is ttx file and then i rename it to .txt file, its format is Tab separated Text and it has "" in it that i have to remove as they come into the database field also..