duplicate entry

Hi!
I tried to install this Node Images module, which seems the one i need to insert a gallery image with thumbnails inside a CCK node; but i get this error message:
user warning: Duplicate entry 'node_images_position_content_ccknode' for key 1 query: INSERT INTO variable (name, value) VALUES ('node_images_position_ccknode', 's:4:\"hide\";') in /web/htdocs/www.mysite.it/home/drupal/includes/database.mysql.inc on line 121.

I am working with the drupal version 4.7.6.

I really hope that someone could help me because i am completely mad about all the modules i've tried to install to add galleries to cck node but every module has something wrong :(