Some odd goings-on with MPA today.In the morning a large amount...

Some odd goings-on with MPA today.
In the morning a large amount of stock was apparently dumped on the market, pushing the price down to 4%.
I bought some - a buy order which had been sitting in the market for quite a while was hit.

Shortly afterwards, Commsec called me and asked me to agree to them cancelling the tranasction on the ground that it was a "mistake" by someone. They told me, if I didn't agree, the ASX would probably cancel the transaction anyhow if the clumsy party beseeched them to.

I see that most of the trades ( except one ) were apparently cancelled.

What was actually going on, remains a big mystery to me.