Iperdesign_IT on "[Plugin: NextGEN Gallery] "Clear image cache" leads to 403"

Hi guys,

with the NGG plugin, clicking "Clear image cache" in "Other Options", it leads me to a 403 Forbidden Error.

I'm using the last version of WP and NGG.

Is it a permission problem? I hope you can help me :)

http://wordpress.org/plugins/nextgen-gallery/