Just to say that we are in exactly the same boat - DD is an excellent napper until the 4pm feed, then she is very hard to settle unless we go for a walk or rock her. No idea why, but she is now 12 weeks and it's slowly getting better... She has gone down in her cot 3 times for her cat nap in the last fortnight, so I guess that's progress. It's definitely evening 'colic' related, and I just tell myself to be grateful that she goes down so well for the other naps and BT, and not to worry that I have to AP once a day at this time... After all, eventually she won't need to nap at that time anymore, so she's bound to grow out of it!