Comment 11 for bug 1499746

If you are using Ubuntu 15.10 Beta 2 (Wily), then the workaround is to manually download syslinux_6.03+dfsg-5ubuntu1 debian package from Vivid repository, extract syslinux binary and use it instead.

syslinux doesn't have other dependencies and other files used when creating a bootable usb (viz.mbr.bin) are identical between Vivid and Wily.

The error is primarily due to ldlinux.sys (which gets generated from syslinux). ldlinux.sys generated from Vivid syslinux doesn't have the issue.