CSV Import needs major help

We get .csv files from companies we acquire to bring in their customers, their contacts and their software licenses (custom record). It may come from SalesForce, manually managed .xls files, Quicken, et al. Without fail, the import process will puke after selecting the file to import due to some number of lines (sometimes hundreds) that have characters it doesn't like for some reason. Often these look like normal American alphabet characters that I can actually fix by simply re-typing (copy/paste won't work). Other times, it's from the extended-ASCII character set. Spanish characters, German, French, other. It doesn't like those. They'll