It could be that there is a checksum mismatch for the disk image, or you experienced a bug in Disk Utility.
You can try to use the
asr command-line utility to copy the image yourself. To do that, you need:
- The InstallESD.dmg image
- A large enough HFS+ partition on an external drive created through Disk Utility, let's call it
- A running terminal
In your terminal, enter the following line, but replace the path to your OS X installer image and the target partition:
asr restore --source Desktop/InstallESD.dmg --target /Volumes/Install
Now, you should get output similar to the following:
Retrieving scan information...done
Copying ....10....20....30....40....50....60....70....80....90....asr: did not copy blessed information to target, which may have missing or out-of-date blessed folder information.
Ejecting the source image...done
Now, you can boot into the installer from your USB drive too. To verify if it worked, go to System Preferences » Startup Disk, and check if your installer appears: