darth_ender said:
I prefer "Captain," as that was also what was used in the novelization, and later Threepio denies any familiarity with her while Luke is checking out her hologram. It doesn't appear he is lying, so I find this to be a mistake. Captain seems to be the original line, and it makes more sense. I'd go with that.
Also if C-3PO did say "There'll be no escape for the Captain this time", if fore-shadows what will happen to him about 5-6 minutes later.