Run all selected optimizations button stopped working

I’m having a very peculiar problem: On one of the sites where I use WP-Optimize, the “Run all selected optimizations” button has mysteriously stopped working. Clicking the button visibly works (I see the button change as its pressed), but nothing happens. The individual “Run optimization” buttons all still work. “Run all selected optimizations” worked fine as late as last night and still works on other sites that use this plugin.

I tried replacing all the plugin files with fresh copies from www.ads-software.com, deactivating and reactivating the plugin, deleting the plugin and reinstalling it, and the same problem persists. (This is with the latest Version 3.0.19.)

Any idea what might be going on? Like I said, it worked properly up through yesterday, and I haven’t added any other plugins or made any configuration changes in the interim. I’m baffled.