There is a vengeance talent called Demon Blades on the second row that changes Demon’s Bite to a passive. What is means for macros is that if you activate that talent and have Demon’s Bite in your macro it will change to Demon Blades and do nothing everytime you get there. If this is in a cast sequence this will hang the sequence.
I cant code around this but you can put the following in instead of Demon’s Bite:
/cast [talent:2/3] Chaos Strike; Demon's Bite
/castsequence spell1, spell2, [talent:2/3] Chaos Strike; Demon's Bite, spell3