"Your bootable usb could not be created" "An error occurred while copying the Windows installation files"

I'm trying to use BootCamp to install Windows 7 on my Macbook Pro. However, I'm having issues because I downloaded Windows 7 from DreamSpark over the internet, so I don't have an 'installation disc'. Instead, I got BootCamp to give me the option to create a bootable USB using the .iso file I downloaded. At first it seems to be completely fine, but midway through it always gives the error message "Your bootable usb could not be created", and under that "An error occurred while copying the Windows installation files"

I followed a topic on this before, but I never found a solution--the closest was a suggestion to unmount the ISO if it had been mounted beforehand. I had mounted it beforehand, so I unmounted it--however, this did not fix the issue.

Any help would be greatly appreciated.