How to change settings of Mantra?

Hi guys,
I decided to change some settings of Mantra (the width of the sidebar and of the main area) long time after creating the site, and found, that now I need the Cryout Serious Theme Settings plugin. OK, I installed it. I played with different values of the width, each time saving and analyzing how the site looks. However, after the 4th or 5th change, I couldn’t save and got an error. I re-opened the Mantra Settings page – now it is looking as it was before (without the “accordion” of settings) and suggests to install the Cryout Serious Theme Settings plugin (which is already installed and activated). I re-installed it, but that didn’t help. Any idea?

The page I need help with: [log in to see the link]