Make sure you have a 32bit version of libusb installed as it clearly is trying to use the 64bit version. That said, with a correctly configured dual 32/64bit system I believe it should just see that its missing rather than trying to use the 64bit library, so you may be running a pure 64bit system without the 32bit directory structure necessarily to have both 32 and 64 bit libraries installed simultaneously. Personally I would recommend simply booting from an Ubuntu Live CD (I used 8.10) and flashing from there. I too am running a 64bit Linux and couldn't get the flasher to work (as it said USB was already in use).
Make sure you have a 32bit version of libusb installed as it clearly is trying to use the 64bit version. That said, with a correctly configured dual 32/64bit system I believe it should just see that its missing rather than trying to use the 64bit library, so you may be running a pure 64bit system without the 32bit directory structure necessarily to have both 32 and 64 bit libraries installed simultaneously.
dpkg-deb -c libusb-0.1-4_0.1.12-13_i386.deb sudo dpkg -x libusb-0.1-4_0.1.12-13_i386.deb libusb-0.1-4_0.1.12-13_i386 sudo mv libusb-0.1-4_0.1.12-13_i386/lib/* /lib32 cd /usr/lib32 sudo ln -s /lib32/libusb-0.1.so.4