Do you have a 64 Gb SD card formatted as ext? If so, you will need to do one of two things:
1) Flash a kernal that supports 64 Gb ext formatted SD; or
2) Reformat your SD card to FAT32.
Other things to try:
1) Make sure you have done a full wipe before installing the ROM;
2) Download the ROM again, in case it was corrupted when you downloaded it;
3) Download to a desktop computer, then transfer it the phone, rather than downloading it directly to your phone. Sometimes this avoids file corruption in download.