In version 0.9.1, when posting a new entry, the "Access restrictions" dropdown does not contain any groups or communities; it only contains the three defaults (public, private, logged in). The "Access restrictions" dropdown does display a complete list when editing an existing entry.
This seems to happen because of these lines in lib/setup.php:
//@rho Force to reload user data from db
$_SESSION['USER'] = new StdClass;
$SESSION = &$_SESSION['SESSION']; // Makes them easier to reference
$USER = &$_SESSION['USER'];
The $USER information is filled in later, when you run("init"), but it happens after the access restrictions dropdown has been populated, so the current user's groups/communities are not recognized.
This same problem does not occur in 0.9.0. (Sorry for the inaccurate version in the actual ticket -- I can't select "0.9.1" in the version dropdown).