Sub-site Plugins stopped working.

Hello,

For some reason, the plugins menus have stopped working on my individual sub-sites. I have to enable them via the Main Admin Panel and even then they show as grayed out and unavailable, even in the “super” admin page menus. I checked off “enable administration menus” in the network settings as well as disabling all other plugins. Is there a MU site directory listing I can look at somewhere? Or should I backup wp-content and re-install WordPress MU? Or are there some other things I can look at?

Please advise.

Thank you,
Brian