default products page getting 503 error

I keep getting 503 errors on my products page in MarketPress. This is a new install of it and I’m testing things to get it all sorted it out. This problem is not unique to a single blog. It is happening on all the marketpress enabled subsites.

Link to homepage of test site:

Link to Store page:

Link to products page (this is the broken one):

While I can always create a work around by manually creating pages and using shortcodes, this is isn’t working out-of-the-box (these are the pages created by the plugin) and my sellers are going to get confused. Any idea what is causing this?