Internet access over usb

so I want to apt-get my debian.ext3 image file in Debian Linux (HostPC).
I followed:http://wiki.mobileread.com/wiki/Inte...Kindle_via_USB

Setup on Host PC Add the following to /etc/network/interfaces

iface usb0 inet static
address 192.168.15.201
netmask 255.255.255.0
up echo 1 > /proc/sys/net/ipv4/ip_forward
up iptables -P FORWARD ACCEPT
up iptables -A POSTROUTING -t nat -j MASQUERADE -s 192.168.15.0/24
down echo 0 > /proc/sys/net/ipv4/ip_forward
down echo 0 > /proc/sys/net/iptables -t nat -F POSTROUTING

Setup in Kindle
echo "nameserver 4.2.2.1" > /etc/resolv.conf
route add default gw 192.168.15.201

I had network-manager, but I couldn't figure out how to have both eth0 and usb0 up at the same time with that, so I disabled and installed wicd. I added "iface eth0 inet dhcp" to the interfaces file and restarted the network service. Both eth0 and usb0 now have IP addresses - so far so good.

Now I still can't ping anything on the internet, so it might be the MASQUERADE thing? Is there a way to trace how far packets go or what?

Next step, please?

edit: pinging from the host to the internet shows my usb0 ip is the one trying to reach the internet, not my eth0?