That's interesting that he isn't actually waking up. My LO makes noise (not crying) at the 45 minute mark but he is awake. Sometimes he can get himself back to sleep. I don't think anything is wrong with your lo. I am assuming he wakes up happy from his nap. Tracy does say in her book that babies make a "phantom cry" while sleeping, so this is why we should not rush right in, because we may actually be waking them. I would just keep going in and making sure he's OK, but try not to move him or wake him up. Has he previously been a good napper?