We've recently tried Ferber's method of progressive waiting to help our 4-month-old sleep better.
At nights, it's worked extremely well... after his bath in the evening he now falls asleep within minutes of being placed in his crib, and usually sleeps through the night with only one feeding, after which he falls asleep again in his crib with no problems.
However, naps aren't working so well. He only seems to be able to fall asleep while nursing. We've tried preventing him from sleeping while nursing, which only causes him to be so tired that at his next feeding he'll fall asleep instantly as soon as he's put on the breast. And he still won't fall asleep any other way, even being held or rocked. We've let him cry in his crib for up to 30 minutes, and his crying only increases in intensity (unlike when we were sleep training him in the evenings, when he'd eventually get calmer).
Anyone dealt with any similar scenarios?