Jim Irwin,
Answers to your questions as follows:
1) The Minister is not accountable.Why ? Pollies are untouchable. If an Aussie passenger jet pancakes into the ground then at worst,the Minister gets shuffled elsewhere.He is safe.Just take a look at the Tinfoil Fairy and others who have made monumental and epic stuff up's.
2) The Director will only get punted if the Minister looks bad or comes under extreme scrutiny or has to endure never ending bad publicity and a heated anti-Minister campaign,that is the Standard Operating Procedure.
3) The Board.They too are safe. You don't become a board member due to skill and experience, it is a 'reward' role for knowing somebody who has a good deal of clout.This rule is applied in any organisation where a Board exists.
4) Blame predecessor's ? Sure,why not.You have to start the deflection process somewhere. And where better to start throwing the blame than at people who are no longer in a position to defend themselves.
And if all the above fails and somebody does have to fall on their sword, then they need not panic,they always get cut loose only after agreeing to a nicely padded severance package which will see them retire comfortably to Sydney's north shore or an island in the Bahama's.