[Plugin: One Click Plugin Updater] Problem with permissions

I installed the One Click Plugin Updater and then used it to install some themes. All the themes installed with this plugin are working fine except the fact that now i can’t delete or modify the folders or change permissions to them. It says “Permission denied” with FTP, and when i tried to delete the themes directly from the wp-admin it said “deleted” but the themes are still there, no changed.

I did a test by uploading a theme through FTP (no use of this plugin) and i can modify or delete it normally. That’s why I think the problem comes from this plugin.