I think its a common problem the more I read these threads. My 2 1/2 yr old is having the same kind of problem. He has always gone on his potty pads, but for the past couple of months, he has gone EVERYWHERE!!
We can never ever catch him in the act...anytime we are home, hes an angel and goes where he is supposed to. We have resorted to "locking" him up in our laundry room when we leave now, where as he used to have free run of the house 24/7. Its very frustrating! We have never crate trained...we used a method where we had a small area fenced off with his tee tee pad and gradually made it larger and larger..I may have to start back to square one there!