Paypal Error: Invalid Regular Period; Membership Premium

I am using Membership Premium 3.0.2 with WordPress 3.3.1. When I try to sign up for a subscription using a PayPal Express Gateway in live site mode, I get the following error: Invalid Regular Period. You must specify valid values for the A3, P3, and T3 paramaters for a subscription. My "Test Class" subscription plan is as follows: Level 1, finite, 1 month, 1.00 USD, Level 2, finite, 1 month, 1.00 USD. The sign up is at http://www.nsama.com/index.php/registration/