After activating camera-slideshow "for all blogs" in a multi-site WP installation, the admin panel is no longer accessible from any user account, no matter what user level. Only the error message "You do not have sufficient permissions to access this page." is visible.
I recommend not activating the plugin in a multi-site installation and instead activate it on each site/blog separately, this seems to work.
If anybody already has this problem just delete the plugin from the "wp-content/plugins" folder or - for good measure - rename the "wp-content/plugins" folder (e.g. to "wp-content/plugins.old").
I hope it can be fixed, this is a very nice plugin.