Portfolio sub category page widths?

First, big thanks for an unbelievable beautiful free theme!

Sorry to bother you with questions, but I have been banging my head with this already several hours. No help from google or this forum (yes, I even went all the 44 pages through!), or my eyes are just too frustrated to see the answers.

So, I have a portfolio page which I have set to be “Portfolio, four columns”. Then, for the articles I have one main category and two sub categories. When I select the portfolio page from landing page, everything is fine. My portfolio items are all shown nicely in 4 columns and width of the page is not changed (remains 1140px). Then, if I press either of the sub category buttons (not menu, but those buttons generated by the sub categories), the page width minimizes itself to 760px! I would like to have it consistent 1140px on all the pages. I cannot figure out what happens there..? Where it should fetch the width in this case? Any advice what I might be missing?

Settings:
Theme Options->Layout->Default Layout Template->Full Width
Theme Options->Layout->Grid Layout Dimensions->4
Theme Options->General->Hard crop post thumbnails->unchecked (and the AJAX Thumbnail Rebuild has been run)

Things I have read:
http://www.mouseclick.com/tutorials-2/setup-a-basic-portfolio/
http://www.mouseclick.com/tutorials-2/add-categories-to-a-portfolio/
http://www.onedesigns.com/support/topic/guide-how-to-create-a-portfolio-with-templates-and-add-it-to-the-main-menue
(Thanks Alexander, really good tutorials)

On your demo page (http://demo.onedesigns.com/pinboard/?page_id=26), the width remains the same after pressing the sub category buttons. Even in case when also in your demo page the amount of columns drops to 3 after starting pressing category buttons.