Continuity mistake: When Chaucer is introducing William at the end of the movie, he stands on the arms between the chairs of Prince Edward and the lady, a foot on each arm. When it cuts to a side view showing William's father to the Prince, Chaucer is no longer in between the chairs. Not to mention the fact that the Prince is looking at the railing (where Chaucer just was). The very next shot, he is back between the chairs. (02:03:05)
Revealing mistake: After a naked Chaucer tells William of his gambling problem, and Simon the Summoner says that he owes 10 gold florins, when Wat angrily grabs Chaucer to punch him we see that Chaucer is actually wearing some type of underwear in the close-up. (00:26:05)
Answer: The reason he is so agitated has to do with the manner in which he won the tournament. If you'll recall, William states, "I'll not be champion until I beat Adamar." Adamar had forefeited beforehand, (not wanting to joust against royalty) therefore not giving William a true victory. After his half won victory, Jocelyn's (Shannon Sossamon's character) inane chatter just rubbed him the wrong way. It had nothing to do with what she was saying...if anyone had spoken to him he would have reacted in the same way.