K., I have a 9 month old son who started the exact thing when he was about 8 months. I took him to the dr. fearing an ear infection, but there was no infection. What my dr. told me was that at about his age he is going through major developmental milestones like sitting up, standing, and the biggie is object permanence. What could be happening, if it's not an ear infection, is that he wants to use all his new skills and wants to be near you (separation anxiety sets in about now too) and can't "turn off" to go to sleep. And then he gets so tired he goes into the second wind, even third wind, and is giddy with energy but exhausted and can't sleep even more.
So, to get my son to sleep we had to shorten the time between naps just a little to make sure we got him down before he was past that twilight stage where he was tired enough to fall asleep. You may have to experiment a little, but start a little earlier than you have been trying lately. I also work a little harder at naptime to get him to go down--whatever you son likes. I sing and we rock until he's pliable and I can lay him down and he doesn't protest. It took a few weeks to be where we are now and have him back on a good nap schedule. If they don't nap well during the day then nighttime sleep can be affected too.
We also moved his bedtime up. We start the bedtime routine at 6 and he is asleep by 7pm. He sleeps through the night now until 6 am.
I hope something here will help you. Hang in there. He will go to sleep easier eventually. If you continue to have problems and it isn't a medical issue I recommend the book "Healthy Sleep Habits, Happy Child" by Marc Weissbluth, MD.
Good luck.