Some of the comments suggest adding ifconfig eth0 down, which did not work for my Acer Travelmate 4500. However I found one that suggested ifconfig eth0 shutdown, which cleared up the problem after I added a line for each network interface. I don't know enough about it to know if one or both are correct (down vs shutdown), but figured somebody else might find this useful.
Some of the comments suggest adding ifconfig eth0 down, which did not work for my Acer Travelmate 4500. However I found one that suggested ifconfig eth0 shutdown, which cleared up the problem after I added a line for each network interface. I don't know enough about it to know if one or both are correct (down vs shutdown), but figured somebody else might find this useful.