Error while creating OS X Mavericks bootable USB
Had the same problem. Thought the file "createinstallmedia" was missing, but that wasn't the case.
Then I realised I simply needed to make it executable with the following command:

sudo chmod +x /Applications/Install\ OS\ X\ Mavericks.app/Contents/Resources/createinstallmedia


This will create the executable that DiskMaker X initially couldn't find. 
After running the command above you shouldn't have the error anymore.

Hope that helps :)