This issue started within the past week and I cant say what specifically caused it as I updated wordpress and marketpress during the past week.
Basically grid view no longer works when using the twenty fourteen film unless store style is set to modern. I have tried using other themes and there isnt an issue so it seems so far to be twenty fourteen it is affecting.
I am currently using a child theme of twenty fourteen and I have tried changing themes to the parent unmodified twenty fourteen and the problem still exists. I even downloaded a fresh copy of twenty fourteen on the off chance I change something and just forgot.
My install of marketpress is un modified I have not changed the plugin in anyway at all except for updates via the wpmu dashboard.
Any Help would be much appreciated and I shall turn on the support access now incase you need to have a poke around.