OS X :: Applications Automatically Switching Spaces?

I use spaces on my Mac and occasionally I use MS Word in one space and Firefox in another. I will constantly switch between spaces because I'm doing research or something else in Firefox. After a few switches like that, when I switch back to the space Word is in and click on the Word window it sends the document window up to the Firefox space. It also occasionally switches the window back to it's correct space. It's very frustrating. Is there anyway to stop this automatic moving of applications? I've looked in System Preferences under spaces and I've done a quick google search but have returned nothing.