Opencv, CUDA problem

I am working with Opencv for a while. Recently, I decided to use Opencv GPU functions which use CUDA to improve performance. I compiled Opencv to be able using GPU features. But when I run my project, right at the begining -before starting the main() function- I get this message:

“The procedure entry point clGetPlatformInfo could not be located in the dynamic link library nvcuda.dll”.

since, exactly the same project works with normal Opencv, do you have any idea what could be the problem? Thanks!
I am using Cuda 5.0, Opencv 2.4.6, vc++ 2010 and windows 7 64 bit. I run it on a system with Nvidia Gforce GTS 450 and the driver is updated to the last version.