A client's blog has all of its plugins deactivated (this happened after a failed upgrade attempt for the Add-to-Any plugin).
Now you can't activate any plugins from the dashboard. I tried resetting the Plugins folder, deactivating them all manually through the database. From the dashboard, I've tried activating them all at once, a couple at a time, and just one at a time. The "Plugins activated" notice appears, but nothing really happens.