I’m having this problem after migrating from one server to another. First, Mantra threw a bunch of errors. I went into the Mantra settings and started doing a 1:1 based on the dev site (which still works fine, running on the same server), and after the first setting was saved (from side-barred to single-column), the slider stopped working. Now it’s stuck at 0px width no matter which layout I select. Even the slider help text says: ^——— Total width = 0px ———^
Running latest wordpress 3.3.2 and mantra v. 1.8.9 as of today.