A strange U B da Judge Problem

aka, The Worst Bidding of the Year

E/W vul, IMPs, short matches

S: KQ9x
H: QJ109x
D: 10
C: xxx
S: Axx
H: Ax
D: Kxxx
C: Axxx
S: J10x
H: Kxx
D: AJxx
C: QJ10
S: 7xx
H: 8xx
D: Q876
C: Kxx

I don't know who held the D:9.

The auction was utterly insane:

North East South West
2H: Pass 2S: Dbl
4S: 5D: Pass Pass
5S: Dbl All Pass

2H: was supposed to be a weak two bid.
2S: was natural and forcing for one round.

The defense slipped...N/S -1400.

a) Apportion the blame between North and South.
b) Which was the least idiotic bid (not pass) N/S perpetrated?

Jeff Goldsmith, jeff@tintin.jpl.nasa.gov, April 1, 1998