I used to join shapefiles and CSV files via the "joins" tool in the layer properties just fine in QGIS 1.8. Now I've updated to QGIS 2.0, and when I do the exact same thing, QGIS puts the name of the CSV source as a prefix in the field name: for example instead of just naming the field "area" it's now labelled "sourcefile_area".
I Googled it, and searched in the QGIS settings, but didn't find anything that helped, maybe I just don't know what exactly to search for though.