hi, thanks for your help!
Yes, i'm drawing the rectangle (as example, i have the same issue with all 2D items), then i'm moving to the box, edit the size (without removing the semicolon or the unit) then pressing enter, but nothing happens.
it's the same way i did on the previous version of sketchup, and it always worked.
The issue is only on the new 2013 version, i still have v8 on the same machine but it's working fine. I'm using the english version for both, i'm not native english but it's easy for me using the same language of the tutorials.

Hi folks, it's my first post here, as i'm a real noob and actually i'm still playing with Sketchup. I tried the new 2013 version, but i can't create precise 2d shapes as described on the help page http://help.sketchup.com/en/article/94837
nothing happens when i'm pressing enter; it also works using the previous versions.
I'm running skecthup on a macbook pro, 10.8 and i already tried to delete preferences and disable all the extensions.
Any suggestion? thanks in advance!