WP E-Commerce breaking bbpress?

I’ve got a stock install of v3.5.1

– Running stock twenty-twelve theme.
– Installed WP E-commerce v3.8.11
– Installed bbpress v2.3.2
– Installed Gravity Forms v1.7.5

Activated Gravity Forms, then WP E-Commerce, then bbpress.

Upon activating bbpress, got an error “You do not have sufficient permissions to access this page.”

If I navigate around the admin, I see that bbpress is activated but none of the menu items (Forums, Topics, Replies) appear and I get the same error when trying to go to the settings.

When I deactivate WP e-Commerce, bbpress works like normal. Is there something WPeC does with user roles that I need to know about?

I haven’t made any content changes to the site at all (no posts, pages, products, forums, anything) it’s a stock install database. Am I missing something that would cause this? I’m sure there can’t be a fundamental conflict between these two plugins as I’m they’re both used on a lot of the same sites.

http://wordpress.org/extend/plugins/wp-e-commerce/