This issue is often caused by either a hardware failure with your drive (as suggested by Error 5, which is almost always an I/O error), or a problem with the disk image you are using. More rarely, it can be a memory error, but this seems unlikely in your case.
You can remedy this particular issue by downloading a clean ISO from the official Ubuntu website, and then verifying the MD5 hash of the file using the below command:
You can find the valid MD5 sums for 16.04.1 below, sourced from this file. Be sure that the results from the command you've run and that file (or below) are the exact same.
After you've verified that the MD5 hashes are actually EXACTLY as they appear here, you may proceed to actually burn it to a known-good flash drive. You can verify a good flash drive by running the read only check specified in the accepted answer to this question.
Once you're sure that both the ISO and your flash drive work properly, you can use the Ubuntu ISO Tool or just
dd to burn the ISO to your flash drive.