What does it mean when your supervisor treats you differently than anyone else on your team?

20 years ago my current supervisor and I had a brief, but pretty hot, affair when we were just colleagues. We had no real contact over the years as we both went in different directions. We weren't in love and to tell you the truth, I don't remember how it ended, but it wasn't awful. Now hes married (happily I'm assuming) and we work together again, only this time he's my boss. He was happy to hire me and I have been the consummate employee. I would never tell anyone about our past and we have never talked about it again. I make sure that I am appropriate in every way, follow his instructions and incorporate his feedback. We have a professional relationship and there are no inappropriate conversations etc. going on. He's sent me some emails thanking me for my work. So, when we are at meetings he compliments other members of the team for their work, but pretty much doesn't acknowledge mine. One-on-one, he's called me and given me lots of compliments and told me that my work is being noticed by his co-workers and the other bosses etc. Of course I'm very pleased to get this feedback, but I'm perplexed about his silence in these meetings. Its happened 3 times now and I haven't (and won't) said anything. Ideas?