Try a carpet cleaner that is made to remove pet odours.
Just thought I would share a story to give you a chuckle. My friend has a cat that is on anti-psycotic medication. One night she came home late from work and had to change her clothes and leave again right away. She had dropped her purse and briefcase just inside the door. The next morning she was about to leave for work and when she picked up her purse it was dripping. The cat had pee'd in her purse. Her wallet, cell phone, palm pilot and everything was soaked. Obviously the cat was angry at her for not being home. After cleaning it all up she was then late for work.
Can you imagine trying to explain that to your boss. That would be like saying the dog ate your homework.