I to use dual screens and have never come up with this problem. Can you please give us more information such as what your operating system is and what is your screen resolution.
Also I would like to note that excel seems to open up in the same position that it was last used. For instance, if I had excel open up in one screen and I closed it, next time I print it comes out on the same screen. Likewise, if the last time I used excel and it took up two screens, when I print to excel it takes up two screens.
So, in my opinion try opening excel on one screen, close it and then print to it. Try to see if that fixes the problem.