With Nextgen activated I have constant unloadings and server drop connections trying to load admin pages and sometimes also front-end pages. Endless loading loops that end up with blank pages on both sides. This serious conflict is at his peak in editing a post.
Two out of three times, when WordPress begins his auto-save, the server goes down and loses the connection, even on the public side: loading attempts lead to blank pages. After 3, 4 or more attempts, pages are only loaded when the autosave ends positively.
I translate the error message:
Connection lost. Saving has been disabled until you're reconnected. We are backing up this post in your browser, just in case.
There's no problem when I save manually.
I also tested this on a site keeping Nextgen as the only activated plugin and I got either the "connection lost" message or an infinite loading of the page.
So, during the "connection lost" message and the pointless loading, without closing the page I tried via FTP to rename the plugin folder to deactivate it at once. Suddenly the upload finished, saving was made and the message disappeared.
Once I put the right name the problem comes back after a while and when I rename the folder again it disappears.
Server dropouts happen without working in the editor as well, sometimes even just by opening a page from both sides. It depends on the server peaks I suppose.
If the server doesn't go down, the load is in the order of 30-40 seconds after the last succesful attempt. On the other hand, if the server goes down, a blank page is shown.
So, I tried turning off WP automatic saving via an action in the functions.php, and this seems to solve the problem. For now I haven't experienced server drops anymore.
This is a temporary solution to me of course, and I don't know if it's a Nextgen-WP autosave direct conflict, or a more general problem when a process is required.