Sorry for the late answer, but to me it sounds like OpenGL is not yet initialized, e.g. you call your LoadTextures method before the window is actually showing up...
That seemed really strange to me, as you are linking against all the windows and opengl related libraries, so I tried it in C::B myself and got the same errors.
After struggling with it a while I found the solution: you have to link to SOIL before opengl32!
I didn't know that the order of the libraries matters at all, but that seems to be the proof Hope that works for you too!