Mac mini (Late 2009) + Yosemite: cannot read CDs/DVDs Hardware: Mac mini (Late 2009)

OS: Yosemite 10.10.2

Problem: cannot read CDs/DVDs, either by internal drive or external drive.

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When you insert any type of CD or DVD, ISO, UDF, HFS, original media or not, the Mac mini tries to read for a few seconds, between 15 and 30, and then ejects the media. Only the blank media remain on the drive, so the Finder when Disk Utility can identify them, but when you try to write something, the disc is ejected.

I've tried several tips found on blogs, but nothing can make the Mac mini read the disks.

I've tried also my external drive, an external USB case with DVD-RW from LG, IDE bus, which works perfectly on my PC with Windows 8.1 and Linux OpenSUSE 13.2, and also works perfectly on my old war buddy, a PowerBook G4.

My Mac mini simply refuses to read discs, either by internal as well as external drive by! Yosemite's fault?

Does anyone have a solution or something that could help me find a way to understand and solve this problem?
Mine did the same, however after purchasing an LG external drive Mac/PC from Best Buy, I am now successful in reading disks. I use the cable that came with it on the back of my Mac Mini USB port. This is the cheaper one, and has flimsy  CD tray, but works.