When saving as a kml, is it possible to keep the style of the QGIS layer? I have tried a couple plugins that have been mentioned on here: qgis2kml ('format not yet supported') and qgis2google2 (crashed QGIS upon activating). Is there anything else?
qgis2kml should do what you want.
I get the same error message as you. You should contact the author to let him explain a bit more which data sources he regards as valid input formats.