Sync Problem with Wifi Shield

I have an arduino UNO. I can upload sketches fine, and everything works as it should. That is, until I connect my brand new wifi shield. I got the shield from ebay, but I believe its exactly like this one, except that mine is red (

I get the same error whether I’m on a mac, or a windows machine. Holding down the shift key while uploading sketches I can get the following verbose output:

Binary sketch size: 3,296 bytes (of a 32,256 byte maximum)
D:\DOWNLOADS\arduino-1.0.4-windows\arduino-1.0.4\hardware/tools/avr/bin/avrdude -CD:\DOWNLOADS\arduino-1.0.4-windows\arduino-1.0.4\hardware/tools/avr/etc/avrdude.conf -v -v -v -v -patmega328p -carduino -P\.\COM3 -b115200 -D -Uflash:w:D:\KEVINS\AppData\build7752554792624809766.tmp\sketch_apr09a.cpp.hex:i

avrdude: Version 5.11, compiled on Sep 2 2011 at 19:38:36
Copyright (c) 2000-2005 Brian Dean,
Copyright (c) 2007-2009 Joerg Wunsch

System wide configuration file is “D:\DOWNLOADS\arduino-1.0.4-windows\arduino-1.0.4\hardware/tools/avr/etc/avrdude.conf”

Using Port : \.\COM3
Using Programmer : arduino
Overriding Baud Rate : 115200
avrdude: Send: 0 [30] [20]
avrdude: Send: 0 [30] [20]
avrdude: Send: 0 [30] [20]
avrdude: Recv:
avrdude: stk500_getsync(): not in sync: resp=0x00

avrdude done. Thank you.

Any suggestions on what to do to fix this or things I might try?
As soon as I disconnect the wifi shield, I can upload sketches just fine…