Doing a md5sum (an equal CRC value between the original and the copy is the simplest way to explain it-for me anyway) is important to verifying the iso was properly downloaded.
You can do it (md5sum)from Kubuntu, you can do it from windows, please look around on how to do it.
Maybe someone can give you a link... I've got to run at the moment.
Burning at a lower speed can help reduce write (CRC) errors.
You can burn disks, they can check out but if you are using a SATA CD/DVD drive to install, things can be really inconsistent with Kubuntu on how it works.