We're finally noticing some strange action in AutoCAD 2013 that we didn't see in 2011. If we have several drawings open, say drawings A, B, C...
1. While in A we issue the "Save" command but leave the drawing open
2. Use the ctrl+tab combo to switch to B
3. Issue the "Save" command here also
4. Then ctrl+shift+tab back to A
5. Try to close it with the "X" in the upper right corner and at this point AutoCAD asks if we want to save the drawing, but nothing has changed since the save.
Actually, if we just open several drawings and toggle through them with the ctrl+tab combo ~without even zooming or changing the view or anything~ just cycling through the drawings, when we try to close them we are prompted to save.