i was kinda suprised that holding on the 'alt'-key when moving around my pictures didn't help placing them precisely anymore, in microsoft office professional 2010 .

so maybe this solution can help others as well:
1) right click on the picture so the tab "Picture tools - format" pops up on the top bar.
2) click on the tab "Picture tools - format" > then choose 'align' > then 'grid settings'
3) now uncheck the first box, which is called 'snap objects to other objects'

this did the trick for me. hope it helps others!