At first I thought it was just with copy/paste but if I type any substantial amount of page content I can't get the page to successfully update :(
I have tried ALL the suggestions in this post here: http://wordpress.org/support/topic/page-wont-update-after-copy-paste?replies=9
* Deactivating plugins
* Switching to default theme
* Resetting plugins folder
* Reuploading new copies of wp-admin and wp-includes
I don't use a caching plugin so not sure why else it stopped working :( not sure when it stopped either as I haven't updated anything on that site for a while!
It's a multisite install and since there are other sites on the network I don't think a clean slate is possible