macosx: create Windows readable partition on your usb

diskutil partitionDisk /dev/disk6 MBRFormat "MS-DOS FAT32" "partition_name" 100%

macosx: burn ISO to USB stick

# first, unmount your USB stick
diskutil umount /Volumes/my_usb_stick/

# convert .iso to .dmg (writing .iso to USB stick does not seem to be creating bootable USB)
hdiutil convert -format UDRW -o ubuntu_12.04_PRE_precise-desktop-amd64.dmg /Volumes/storage/Software/Distros/ubuntu_12.04_PRE_precise-desktop-amd64.iso

# write new image to USB
root# dd if=ubuntu_12.04_PRE_precise-desktop-amd64.dmg of=/dev/disk1
1434200+0 records in
1434200+0 records out
734310400 bytes transferred in 3514.831504 secs (208918 bytes/sec)