Can't burn a CD, files keep getting locked

I have a 2013 iMac and have upgraded to Yosemite.

Everytime I try to burn a cd on my Apple external CD drive, the CD filed gets locked by the operating system, and it won't let me burn the images.

I am trying to burn photos from my digital camera to a CD.

Why can't I burn CD in Yosemite?

Friggin annoying. Anyone have any ideas? These are new blank C

Thanks

Allan