On top of possible medical or nervousness causes, there is always the "revenge" cause. We used to have a dog who, if we did something she didn't like, peed to get even...no kidding, she'd even look us squarely in the face and then do it.
Not saying that your dog is trying to be mean, but sometimes they do get upset over changes that occur in
their territory, especially when those changes involve a change in
pack dynamics.
Also, I'm sorry if you answered this already, but is she peeing while you are home? Or does she do the deed when you are gone? If it's while you are gone, then you might want to consider crate training for when you're out of the house (also used to housebreak puppies). We currently have a dog who has to be crated when we are out because he will pee everywhere if he's left out.
When we first got him, he also peed when we came home; it was a submissive behavior when he came to greet us. We broke the behavior by only passively greeting him when we first came into the house. A quick, "hi Bear," to acknowledge we were home and he wasn't shunned from the pack, then we would go put our things down, and then we would calmly greet him at his level (crouched down) so that he wouldn't feel intimidated.
Don't know if any of this will help you, but maybe it will. I don't know. Good luck on solving the problem behavior...where's Cesar Milan when you need him?
EDIT: :Nevermind, I reread your posts and surmised that it was being done while you were home...