I skipped the screencaps. Now that there's a clean version of the trailer available, some folks have already made icons. *points at shiny new icon*

And now that the audio is so much clearer, I'm guessing honorat is right. It looks like Jack is doggin' Liz.

As to why Will would be ready to let Norrington kill Jack - and I've not read any spoilers about this bit - I'm guessing it has something to do with "Bootstrap" (now "Barnacle") Bill Turner. :p