My multisite was fine yesterday and in between I havent done anything new or that I shouldnt have ie new installation of plugins/themes etc.. In fact I havent done anything major or minor for a 4/5 days now at least, maybe a week. And all has been fine, up until today...
Today, all multisite users have lost access to their sites and are not listed in multisite admin as being associated to their sites. If I manually add a user to a site, I get the yellow "User added" message at the top of the page, but they are not added to the sites user list (and the users not added to the sites list either) and the user cannot log in to the site but gets the global dashboard instead like a standard user only account, and not their own site dashboard. I cannot even add the superadmin to a site's user list (which appears to be completely blank), again I get the yellow message but nothing then showing in the lists that this has been done.
Any help/ideas much appreciated.