Yep, when I change to /%postname%/ it works but I prefer my permalinks to start with a numerical item to keep up the speed.
/%post_id%/ does NOT work and /%post_id%/%postname% does also not work
Qoute: "For performance reasons, it is not a good idea to start your permalink structure with the category, tag, author, or postname fields. The reason is that these are text fields, and using them at the beginning of your permalink structure it takes more time for WordPress to distinguish your Post URLs from Page URLs (which always use the text "page slug" as the URL), and to compensate, WordPress stores a lot of extra information in its database (so much that sites with lots of Pages have experienced difficulties). So, it is best to start your permalink structure with a numeric field, such as the year or post ID."
from here: http://codex.wordpress.org/Using_Permalinks