You are not allowed to create a review.

I've become a member of the Gamespot community, rated a couple of games.

But suddenly when I try to rate a game, a message "You are not allowed to create a review" appears.

What can I do to be able to rate again ?

This may be related to the new user restrictions, which are mostly lifted once you reach 25 total posts (you can only post 5 times a time until you reach 25 total as well).