Shopping cart and other virtual pages redirecting

Hi all,

I'm on WP 3.0.5 and BP 1.2.7 with a multisite install. I've searched and read all related posts but am still stuck.

I've installed marketpress and can't get the shopping cart, products or order status pages to load. When I click on a link for one of those pages, it sends me to the site home page. I can see the shopping cart widget, I can add products to the cart, and I can clear the cart, but I can't check out - it just sends me to the home page.

Per other support postings, I've tried the following:
- changed the shopping cart slug in the Presentation tab of Store Settings and saved several times
- de-activated and activated marketpress plugin (both in network and non-network modes)
- de-activated multi-domain and domain mapping plugins

Interestingly, I couldn't load the Store page until I followed the "Edit Page" link in the Messages tab and then published the page.

Is there something simple I'm missing? Could really use your help as I'm operating on a deadline.

Much Thanks