hi, A.!
i hope my two cents helps a little! i have a now 19 month old little guy and he, too, started having problems sleeping through the night (but around 13 months) and i got onto the baby whisperer forum page (i just love these books...they really helped me!) and realized that maybe my guy was ready to drop the morning nap. what i did was put him down for his morning nap at a later and later time...so, instead of 9, i'd put him to bed around 9:20 for a few days, then stretch it to 9:45 or so for a few days, and so forth. i tried to keep the afternoon nap around the same time, but i didn't let him sleep for longer than 1.5 hours so that he would be tired for the night! then, eventually, when we were about an hour or two between naps, i'd just keep him up by taking him to the park or doing something novel and then put him to bed at 1 pm. some kids have to go to bed at noon. once we started my little guy on just one nap a day (his is from 1 to 3), he started sleeping all night again.
i hope this helps! it does sound like he only needs one nap because he is waking up and wanting to play!
good luck!
-B.