Hi and welcome to Just Answer! My name is XXXXX XXXXX X will be happy to help you with this.
I will need some more information first. What type of disks are you using? Brand, speed? Is the DVR getting unusually hot durring this process?
Unfortunately these disks are quite picky. They don't like certain types of disks and you will get the "Dirty disk" error a lot when using any brand but Sony. (Go figure, huh?)
I would attempt to use another type of disk first, preferably Sony.
I would also get a lens cleaner disk and run that as well.
That will rule out the cheap simple stuff, and if you have more trouble please reply here and I will be happy to assist you further.