Class doesnt know GLEW function

Hi,

i have a problem with loaded glew functions.
I had been trying some vbo code in main function only, i had loaded functions like glBindBuffer there aswell.
Now i wanted to use those functions in a included class but the class doesnt know them.

It's like:

// Include stuff

main function
{
initializing
load glew functions like glBindBuffer, glGenBuffers and so on
create renderwindow
call class method using glGenBuffers -> crash caused by glGenBuffers being NULL, why?
}

I load those functions like this: PFNGLGENBUFFERSPROC glGenBuffers = (PFNGLGENBUFFERSPROC) glfwGetProcAddress("glGenBuffers");

Now i dont know why the class can't call the function although it is loaded, i used those function before directly in main function for trying.

What is my fault?

Thanks!