External CD burner won't recognize blank CD

I have a brand new CD/DVD burner from Memorex that plays pre-recorded CD's just fine, but when I put in a blank CD - it seems like the blank CD isn't recognized. I’ve been reviewing logs and I don’t see any evidence of an error. The current default behavior when a blank CD is inserted should be to open iTunes. The focus does ship to Itunes, but nothing else happens. Also, the CD doesn’t show up in the Finder, or on the desktop. Once the CD is inserted into the optical drive, the eject button on the unit becomes inoperable. (It works fine with pre-recorded CD’s.) The only way to eject a blank CD is to either restart the computer, or to open the Disk Utility program and eject it from there. The Disk Utility seems to be the only application that is aware of the blank CD - though it reports that the capacity is 0 kb and is unitialized, and that both the partition map and SMART status are shown as “Not Supported”. I've tried this with two different brands of CDR's and get the same problem.

Note that I get this behavior on two new Imacs. The first is a retinal 27" machine with 16 GB of RAM, and the hard drive with more than 2 TB of space remaining. The other machine is a non-retinal 21" iMac with 8 GB of RAM, and about 500 GB remaining on the hard drive. Both machines are running El Capitan.

This is the 2nd optical drive from Memorex that has given me this problem. I returned the 1st under warranty, and just received the replacement unit in the mail this morning. I contacted Apple tech support, who were very nice. They took me through an SMC reset, but this had no effect. Apart from them, they had no clue as to what was causing the problem. I thought I'd try to write to you geniuses. Any ideas? Thanks in advance.

--david