Strange Flash CS4 Issue

don’t know what trigger this on my Flash CS4, suddenly i cant see any object on my stage it just plane background and i can change its color, but when i start to draw i can see the initial drawing but when i release the mouse the object is gone, try to test the movie and the object is there. i try to close the program and open again but still the same until i discover that this behavior happen when my publish setting is set to action script 3.0 changing it to 2.0 and the problem goes away. i did not encounter this kind of behavior with as3 before.

can any one knows about this?