It was my Graphic card. Thanks for the help!

Hi, First... Sorry but i don't speak english very well ! (or... i must say i don't speak english at all !!!!) When you move one object over another object (the 2 object corners are touching each other) , for exemple, you move a cube#1, selecting a corner and you drop it (move it) until the corner is touching a corner from cube#2, there is no problem... You can zoom at maximum, the 2 corner of the cubes are always at the same point (same place). Now you repeat the same operation but before you move the cube, you make a group (or component) with each cube... You can move cube#1 (corner from cube#1) on the cube#2 (corner from cube#2) selecting "end of component" or "end of group" to snap... but when you make a zoom at maximum, you see that the 2 corners are not at the same place !!!! The difference is very very small... but you see that the 2 corners are'nt in a same location. I have search for a long time because this "detail" is for me not acceptable... But... now if you explode the two group (after you have move them) and after that you zoom at the maximum, the 2 corners are NOW in the exact and same location... Conclusion : when you work with component or group, visually Sketchup can't display the object at the right place... The object (group or component) are in the right place but when you make a big zoom, Sketchup cannot display them correctly... Sorry... I hope you understand what i mean...