Haven't seen this specific issue in the other Marketpress pagination threads. On default generated category pages the pagination works, but using shortcode it doesn't. I've tried this with and without parameters with no luck. Not using any custom page templates or functions. Site is still under construction, but you can see the difference. There are 20+ products in this category.
Default cat page - http://brocka.net/blog/shop/products/category/games-and-accessories/
With shortcode - http://brocka.net/shop/games-and-accessories/