Well, in the GENXML, in field SQL, use only this:
queryvideodatabase(select distinct idartist,c10 from musicvideo join artistlinkmusicvideo ON musicvideo.idmvideo=artistlinkmusicvideo.idmvideo)
To generate the XML file, XBMC should be active, running...
In XBMC, check in Settings ->Option NETWORK ->
Allow Control XBMC via HTTP - SET ON
Set port : 8080
Username and password, equal in XBMC and voxcommando, for work, or set blank for 2 fields.
save, and try again