First off CS5 is unsupported under 10.10 but I doubt that’s the issue.
You should be using AI or PDF from Illustrator and when you show options choose transparent background.
DO NOT USE EPS! It’s an archaic format.
Show import options and change it to transparent background. It will stick until changed again.
Bob and Peter;
Of course! Thank you both. Bob's answer came in a few milli-seconds before Peter's so Bob gets the Correct Answer citation.