There is way too little information here to help diagnose the problem. When seeking help with debugging run-time failures, it is highly advisable to post buildable and runnable, self-contained code that reproduces the problem, so others can experiment with the code. The smaller the code the better. Also you would want to mention how the code is compiled (exact nvcc command line) and on what GPU and OS platform you are running the code.
In any case, make sure that your code checks the status return of every API call, and every kernel launch, otherwise it can easily happen that the source of the problem is far away from the point of failure, and much harder to find.