QSPI - SD card interface

I am working on an SD card interface with an MPC555

I've set up the level transfer using a 4bit bidirectional TI TXB0104
http://focus.ti.com/docs/prod/folders/print/txb0104.html
with the A side at 3.3V and the B side at 5V

I checked the levels at the inputs of the SD card and it seems to be
working ok

I've tried all kinds of timings, but can't get anything out of the DO
pin on the SD card.  

according to the SD card docs, the following should happen

Power up SD card
clock the card for at least 74 cycles at 400KHz with CS and DI high
pull CS low, send 6 byte command
keep CS low while clocking and wait for response (

DO just stays high the whole time.
i've set CPOL=0 and CPHA=0, but I've also tried CPHA=1

the whole set is done in one queue transaction so that the CS stays
low between data command and the response

Any ideas?

Ben