Subscription Plans

I've added the membership plugin and am in the process of setting up the subscription plans. However everytime I add a new subscription I am not able to activate it. Then when I try to delete the Subscription I am not able to delete it. If I go back to edit the subscription and re-enter the membership levels and try to add it I get the message "Are you sure you want to do this?" "Please try again"

Any suggestions?

Hector