Typically this is going to be a PHP memory issue as David has stated above.
Why does it work on another one of your sites and not this one? Easy, they are different sites. They aren't the same site, they could be running different themes, different plugins, etc. Even on Multi-Site as sites can have themes and plugins activated individually.
I don't think deleting sites is going to resolve anything if it's a PHP memory issue related to not enough available PHP memory on the server to allow you to perform the AJAX action that saves the form.
You mentioned your PHP memory setting is currently set at 64M. That is NOT a lot of PHP memory for a standard WordPress install... let alone a Multi-Site installation with 100 sites created. Multi-Site demands more memory, and the amount of memory you'll need will vary depending on the complexity off themes and plugins being used.
I would suggest increasing the available PHP memory to something much higher. 128M or 256M or more. Then give it a try.
Posted 7 years ago on Friday November 2, 2012 | Permalink