What was the GoF error that caused JKR so much trouble?

[cynthiaanncoe at home.com]

No: HPFGUIDX 24953

I've searched and searched, and I can't find a discussion of this.  
As I understand it, JKR was writing GoF and was about half through 
when she noticed a plot problem.  She went back and fixed it.  It is 
something other than the wand order. 

Has the group decided what it was?  I apologize for raising this, but 
I need someone to point me in the right direction.

Thanks.

Cindy
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"And Mr. Crouch evaporated, did he?"  said Hermione coldly.  GOF, Ch. 
29.