Edit: Ignore this, got it working. There was a problem with the instruction bytes.
I'm using SPI to connect an Arduino Pro Mini to an Atmel AT25040B NVRAM chip, and the SPI isn't working properly. I've put a scope on the lines, and all appear to be OK except for the MISO, which seems to be picking up crosstalk from the SCK, but otherwise never changes. The circuit is currently on a breadboard.
I'd welcome any suggestions!