We're going through the same thing with our 4 month old daughter Kasia. (I posted "Could Naps Be Ruining Nighttime Sleep?")
I know that Tracy's book says to enforce daytime naps, and believe me, I worked hard at making them happen and have enjoyed all the free time they afford me, but................
Yesterday Kasia had a morning nap of approx. 30 minutes, a 1 hour afternoon nap and a 15 minute catnap in late afternoon (compared to the two 2 hour naps and 30-45 minute late afternoon nap schedule I had so strictly enforced the week prior). Well, last night she woke up only once, instead of the 5-6 times she had been waking before, which makes me believe that her long naps were indeed affecting her nighttime sleep. So, this week I'm going to try to limit her napping times and see what happens. I'd much rather have her up with me during the day than be up and down and up and down with her all night! I was turning into a zombie and the patience factor was getting pretty slim too!
Even though we're told that our babies should have a certain number of naps per day that last a certain amount of time each, not all babies will conform to one idea. Maybe our babies will just do better with less sleep during the day. Just keep trying different things. Someone once told me about babies: "Just when you think you've got a good routine going and you've got them all figured out......you don't."
Good luck, you're not alone!
Kara