And that happens no matter what size Fireworks document you're using? That's odd. If this is a recent thing, perhaps clearing the clipboard could somehow help.
I'm on a Mac and find that pasted items are placed at 0,0 if they were copied to the clipboard from another application or as a screenshot. If the item is copied from within Fireworks, it pastes at the original X/Y location.
Of course, if you import a bitmap, you can choose exactly where to place the item using the cursor.