Upload over ethernet

Hi all

Looking for some help please. Using an Arduino Uno and an Ethernet Shield (R3) I've followed the instructions at http://www.freetronics.com/pages/how-to-upload-a-sketch-to-your-arduino-via-a-network#.UZJYeLUXaSp to enable uploading of a sketch over my local lan. Everything seems to work fine except when there is a SD card in the slot -this stops the bootloader loading (and therefore accepting a new sketch). I have to pop the SD card for it to continue.

Anyone encountered this? Is it fixable?