Cannot open blank DVDs under 14.04

[Phil]

Thank you for reading this.

I've spent most of the day trying to install Xubuntu on a friend's 
laptop that is currently running a very sick version of Vista.

I have two laptops; one runs Kubuntu 14.04 and the other Xubuntu 14.04 
but neither will detect blank DVDs. They both will open pre-recorded 
DVDs, so the drives are not faulty. Both had version 13.04 installed 
previously and did detect blank DVDs. So either I have missed something 
obvious or 14.04 is the problem.

My Kubuntu laptop has Vista installed as well and it will detect blank 
DVDs. So I installed unetbootin under Windows, which was an exercise in 
frustration in itself, but unetbootin does not see my USB DVD drive (the 
internal drive is faulty).

My friend wants to throw the laptop into the bin but I'd like to show 
that Linux can save a little bit of landfill. So, can anyone suggest why 
both of my DVD drives cannot see a blank disc but can see a pre-recorded 
disk? One of the pre-recorded disks was recorded under 13.04 on the same 
USB disc drive.

-- 
Regards,
Phil