Listname can (depending on list type) be either the internal name of the list, or the GUID of the list.
The later seems to work always so check the GUID by invoking the GetListCollection web service with a web service tool like webservice studio, SOAPscope or similar. You can also obtain the GUID by clicking "modify settings and columns" and checking the URL in the browser (same goes for views, just click the view you want to see).
For the webmethod in question, you dont need to specify a view name, so leave that blank unless you got a special filtered view you want to query.
hth
//AndersR