Drupal 7.10

Logged in as administrator, all permissions ON.

This error was due to the fact that nodeaccess wasn't configured yet. After configuring the module, the behaviour was as expected.

When opening the Grant tab on a page (BEFORE configuring nodeaccess) I get following error on top of page : (I have a total of 5 roles, including unauthorized)

Notice: Undefined offset: 4 in nodeaccess_grants_form() (line 577 of C:\UniServer\www\drupal\sites\all\modules\nodeaccess\nodeaccess.module).
Notice: Undefined offset: 3 in nodeaccess_grants_form() (line 577 of C:\UniServer\www\drupal\sites\all\modules\nodeaccess\nodeaccess.module).
Notice: Undefined offset: 2 in nodeaccess_grants_form() (line 577 of C:\UniServer\www\drupal\sites\all\modules\nodeaccess\nodeaccess.module).
Notice: Undefined offset: 5 in nodeaccess_grants_form() (line 577 of C:\UniServer\www\drupal\sites\all\modules\nodeaccess\nodeaccess.module).
Notice: Undefined offset: 1 in nodeaccess_grants_form() (line 577 of C:\UniServer\www\drupal\sites\all\modules\nodeaccess\nodeaccess.module).

Then it immediately shows the text :
"You can set grants per users. Enter a name or a partial name in the box and click Search or press return. You need to check the Keep? checkbox if you want to keep the user for granting. Note that user grants are additional to those coming from roles.

Enter names to search for users:"