Had this problem myself since switching to Win7 with Office 2007 so decided to look into it. Whilst some of the other solutions that appear in this thread may work for other, I think you have a similar problem to me. I've tried all of the suggestions to
no avail. There isn't any pattern to the moving icons on my desktop. I copy files from our computer network to my local drive (I work remotely from the office so this speeds things up for me). When saving the file it may leave the icon in the same place or
decide to move it to the next available location. There isn't any pattern to this (file type, auto arrange, grid align etc) so therefore it must be a timing thing.
What appears to be happening, is that when I save the file, MSWord is sometimes trying to carry out a background save simultaneously. Saving the same file simultaneously has to cause a conflict with the icon location. This is the reason the icon moves. The
reason for the icon not moving is simple. MSWord isn't trying to carry out the background save at that particular moment and hence no conflict, so the icon stays in the same place. This is why it all appears so random.
The solution is to switch off background saves (Click the office button from within Word, then Word Options, then Advanced. In the Save section you should find the "allow background saves" box ticked. Untick and it should resolve the problem. This does mean
that background saves aren't carried out, but looking at forums etc. no-one actually really seems to know what this function does. It isn't auto recover, so I think you are safe in case of a system crash. My advice though would be to monitor this over a period
of time and carry out plently of manual saves especially when working on large docs.