Krakatoa said:
I'm pretty sure Greedo and/or Jabba were speaking Quechua, just with gibberish sentences. Similar with Lando's copilot in Jedi (I think one of his lines translates as "A thousand herds of elephants are on my foot.")
I think the ROTJ commentary on the DVD says that Lando's copilot's lines actually translate well from whatever African language it's in, and in that country the theaters would erupt in applause when they heard their own language.