These two things I know of that causes the prayers to be not rewarded for 40 days. But, the person still must pray and he/she won't have to repeat the prayer after 40 days.
Whenever obligatory Salah is performed, it produces two results under normal circumstances:
1. It removes the obligation of prayer from that individual.
2. It earns him reward.
In the above cases, it only removes the obligation, but it is devoid of reward.
This is what I have read with regards to visiting fortunetellers.
Allah's Messenger said, "If anyone drinks wine Allah will not accept prayer from him for forty days, but if he repents Allah will forgive him. If he repeats the offence Allah will not accept prayer from him for forty days, but if he repents Allah will forgive him. If he again repeats the offence Allah will not accept prayer from him for forty days, but if he repents Allah will forgive him. If he repeats it a fourth time Allah will not accept prayer from him for forty days, and if he repents Allah will not forgive him, but will give him to drink of the river of the fluid flowing from the inhabitants of Hell."
[Tirmidhi transmitted it, and Nasa'i, Ibn Majah and Darimi transmitted it on the authority of Abdullah ibn Amr.]