FWIW, you're dealing with a man-made machine and man-made code. The list of possible problems is most likely endless.
To help minimize that possibility:
Verify the md5 checksum on the ISO once it's downloaded.
Burn the disc at a SLOW speed for optimum data integrity.
Read the instructions in their entirety
to insure that you understand each step before
attempting the upgrade process.
And ALWAYS back-up your data before performing system changes.
Cheers and good luck!