Cart PHP error + CSV Question

I'm testing the PP Express checkout live. Everything works, but I'm getting a php error after checking out. It persists on subsequent pages.

Warning: Invalid argument supplied for foreach() in /home/username/public_html/wp-content/plugins/marketpress/marketpress.php on line 2057

Also, is there a way to manage a store's inventory by importing and exporting csv files?

Thanks in advance.