Can't reach payment page

Hi...I have installed the latest release (3.0.5) of Pro Sites and network activated it on my WP 3.3 network. I have configured the gateway to use Paypal express, and gone through all of the other configuration options, setting up my levels, premium themes, and plugins. I have set up a 14 day free trial, and have 3 modules enabled (Premium Plugins, Premium Themes, and Premium Support).

However, when I go to add a test site, the site is added fine. However, when I click on Your Account->Your Account, I get redirected to a URL similar to http://www.mydomain.com/pro-site/?bid=6. I see an option to choose the site to upgrade, but clicking on that link does nothing. Also, if I go the Network Admin area, Pro Sites->Pro Sites, and enter the site ID, I see under both Subscription and Subscriber Information this message: "This site is using an older gateway so their information is not accessible."

How can the subscriber be using an older gateway, if I have only had Paypal active? I never used this plugin when it was called Supporter.

More importantly, how come I can't reach a screen similar to the Subscription Selection shown in the installation & use instructions (the 3 x 3 grid of levels and prices)?

I am using W3 TC, but I have tried with that de-activated and no different results. I am also on Nginx (not apache). Do I have to create any special re-write rules?