Official WiFi Shield SPI Communication Problem

Hello Everyone!

I've been waiting for the WiFi Shield for a long time, and it works perfectly on its own.

However, the terminal gives me the message 'WiFi Shield not present" whenever I wire a module up via SPI. For instance, I connected the popular nRF24L01+ module from Sparkfun (https://www.sparkfun.com/products/691?) using the following pins:

MISO 12
MOSI 11
SCK 13
CSN 9
CE 8

Whenever I disconnect pin 12, the shield works just fine.

Is this an SPI problem? Is the module drawing too much current from the shield? Any ideas?

Attached is also an image of my circuit, just for reference:

I believe the shield using the SPI protocol as well. However the Slave Select pin is 10, and pin 7 is used additionally for a handshake.