The NYTimes article says that the initial offering of BATS "would have been the first company to be listed as well as traded on the exchange", and the post mortem currently at the top of http://www.batstrading.com/alerts/ (no direct link that I can see) says that the A-BFZZZ shard "encountered a software bug related to IPO auctions".
I read that to mean that this is the first time they've ever used their IPO-related code in production and it failed badly. So it sounds like it was the normal sort of bug, in their own code, and their own IPO directly triggered the bug.
I read that to mean that this is the first time they've ever used their IPO-related code in production and it failed badly. So it sounds like it was the normal sort of bug, in their own code, and their own IPO directly triggered the bug.