The tabular data (.csv file) and the data in the attributes table of the vector (.shp file) I am trying to join includes accented characters - they are place names in Pamana. For example 'Río Abajo' and 'Curundú'. The problem is that when I import the csv file as a vector file QGIS can't seem to read the accented characters and puts a little '?' instead for those characters. So I just get NULL values appearing in the joined attributes table - all the data for the unaccented names turns up perfectly. I have tried changing the names to unaccented latin characters, from the earlier example 'Río Abajo' becomes 'Rio Abajo'. But then the names don't match up with the place names already in the attributes table of the shapefile I am using (administrative areas for Panama) so the NULL values appear again. Hope you can help.
You do not write which QGIS version you are running. QGIS Lisboa has a bug in encoding utf-8 data, while earlier and newer version should handle it right.
You may find some workarounds here: