Thanks DJA. This puzzle has baffled me. I have solved all the clued lights and am fairly certain of 3 the 8 unclued lights and reasonably sure of another 4 of them, but am unable to find a common feature which they do not share with any clued light. I *so* wanted it to be the single or mutliple appearance of a particular letter, but no joy there. I have no idea how the title could help, but then again I didn't twig to "ACE NTR" either. Will just have to hope for a sudden "Eureka!" moment...