For European accented languages, check that the CSV file you import is encoded in UTF-8. If you want to import asian languages, you will have to encode the CSV in UTF-16.
The easiest way to encode a CSV file in UTF-8 on windows is to open it with the notepad app, then hit the "Save As" menu and choose UTF-8 at the bottom of the screen.
On Mac OS, I use BBEdit, or it's free brother, TextWrangler. See Bare Bones Software | Products
Please look up the UTF8 upload instructions.