There are a lot of unresolved questions surrounding Prometheus, but now there's one less. Spoilers ahead.
In the scene where David addresses the remaining Engineer, he talks in an unfamiliar language that we later learned was a combination of real languages. And now, that bit of conversation has been translated.
The Bioscopist notes that when David is learning the "building blocks" of language, a hologram appears to teach him Proto-Indo European Linguistics. The man in that hologram is Dr. Anil Biltoo of the University of London. The Bioscopist located Biltoo and acquired this translation:
Here's the line that David speaks to the Engineer, and the consultant's translation of it:
/ida hman?m a? kja nam?tuh zd?:taha/…/gh??vah-pjorn-?ttham sas da:t? kredah/
A serviceable translation into English is:
"This man is here because he does not want to die. He believes you can give him more life."
Biltoo also revealed that there was a much longer conversation filmed that was eventually cut for the final edit. But we will have to wait for the DVD to see if Ridley Scott decides to include it among the director's cut or deleted scenes.