2 sites now running very slow had to disable Nextgen

I have 2 sites that now cannot run the latest version of Nextgen, when activated it takes around 2 minutes for the site to load. On my site I have gone back to an older version and that works ok, but now on the other site I helped design they have updated and now its running very slow, I rolled it back to an older version but the admins keep updating to the new version. Any ideas what I can try other than rolling back? I might have to find another plugin for our pictures but I dont want to I have hundreds of pictures to roll over if I do…

Additional both sites running different themes and not many plugins in common and disabling the plugins make no difference..

Thanks!

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