ubercart invalid purchase

I have an issue with a site that I'm working on right now with Ubercart. When somebody is logged in as some form of authenticated user, any attempt to go to an e-commerce related page (product pages, shopping cart, checkout, etc.) gets a redirect to a page called invalid_purchase# I haven't the foggiest idea of why this is, but I need to fix it. I'm using D7. As always, any suggestions are greatly appreciated.