Dear Benjamin,
Thanks for reporting this issue. I have tried replicating your issue with only Types, Views and Installer plugin enabled. But "Add Another Term filter" works (see screenshot). What specifically did not work? Can you mentioned the details how you encounter this error. Also can you please attached screenshot showing the error or copy the errors you see in your JS console. You can see the errors in the JS console using Firebug in Firefox: http://getfirebug.com/
So if you deactivate installer plugin, the problem is resolved?
Cheers,
Emerson