I purchased Nature's Miracle at Petco and the problem has been solved. I treated the area with the solution full strength and then added to the carpet shampooer. Its the only thing that I've found that will break down the enzyme crystals in the cats urine. I HAD a female that did her business all over the basement, even though she had a clean box. :O It even took the smell out of the concrete floor. YEA!!!!!!
Good luck, I know its extremely annoying!