Hi Sorin,
Thanks for your post.
1. Try to edit your New Menu Item from backend and hit save.
It didn't work

2. If no success, purge URL cache from your SEF component or toggle settings of Adsman of your SEF component in Extension Settings.
It didn't work
BTW, "New Ad" link doesn't work with sef off as i wrote in my first post and this is the only link that doesn't work (i get blank page) with sef on or sef off
Regards,