Can't change frontpage with Gridmarket


I've followed the Theme Tailors guide for setting up an Etsy style marketplace. I have the Gridmarket child theme installed with Marketpress. I was trying to get products setup in a sub-store to show up on the main store frontpage but, whilst doing so, discovered that I can't infact make any changes to the frontpage.

The main site frontpage just shows the default:
Our products
No Products

If I go into MySite > Settings > Reading and try selecting a static page as the frontpage it has no affect on the frontpage at all.

Also, if I click on other links on the page, such as 'Hello world!' in the footer, the URL in the browser changes to that of the post but the content of the page still just shows the default frontpage 'Our products'.

The same thing happens when clicking on Archive 'September 2012' in the footer or Categories 'Uncategorized' in the footer.

It's got be totally baffled!