I think the rift was caused by william pointing out megzit's dodgy past regarding allegedly being a yacht girl (among other things), but Harry didn't want to hear those things.
I recall reading that after the engagement was announced a courtier told Charles they needed Harry's decision on some minor royal matter and Charles replied "No point in asking Harry, he's cunt-struck at the moment." and Charles made the decision.
Apparently Chas is rather fond of the word cunt. I bet he's using it a lot more at the moment.