Hi AlexT,
Have you ever read this post by Rexi98 on ESG thread on computerised trading, enlightening though provides very little comfort. I would say it is very relevant to PLA over the last 10 days actually i think its something that we see with PLA regularly.
http://www.hotcopper.com.au/post_single.asp?fid=1&tid=1116235&msgno=5097919