Ever had a plugin that worked wonderfully in “single site” WordPress, but when switching to multi-user mode (WPMU), it doesn’t work on any other site than the initial site? Here’s why. And even better “there’s a plugin for that!” This handy plugin will make some of those stubborn plugins work beautifully under WPMU.
http://wordpress.org/extend/plugins/proper-network-activation/
From the plugin’s page:
When running WordPress MultiSite, you have a very handy feature called network activation. It allows you to activate a plugin for the entire network of sites. The trouble is that it only does half the job.
Some plugins have an install procedure that is meant to be run only on activation. However, when you do a network activation, that install procedure is only run for the current site. So, you end up with plugins not working properly on all the other sites.
What this plugin does:
- when doing a network de/activation, it triggers the de/activation hook on all sites in the network
- when creating a new site, it triggers the activation hook for all active network plugins on that site