@birdog123 – There can be a lot going on in a Multisite installation and you have provided very little context for the error message you are seeing, but as it is there could be a plugin conflict going on here or at least it should be ruled out. Have you tried deactivating all of your plugins, clearing your browser cache (and site caches if you are using a caching plugin), then reactivating the NextGEN plugin?
If this fixes the problem then it was likely one of the deactivated plugins that was causing an issue. Now, retrace your steps activating each plugin and re-checking to see if the problem returns. If it does then that last activated plugin was probably the one. Keep reactivating and in most cases it is also best to keep checking after each plugin, sometimes there may be more than one plugin on a site that will create an issue. If you do find one (or more) plugins causing this problem we would greatly appreciate your feedback on them so the developers may address them as soon as they can.
If the problem still persists after all of this we would still want to know, even more so, as we will still want to sort out the issue and may need additional details.
Thanks!
– Cais.
