I have the same problem. I can download free apps just fine but cannot PURCHASE any. I log into PayPal, verify the funds, then get the error id 30402. "Can not connect to the payment system." I've contacted both Blackberry AND PayPal and each party says to contact the other. Has anyone found anything out since this topic first posted?
Hardware: Blackberry Storm 9530
Software: OS 4.7.0.148
App world version: 1.1.0.20
Go to your Paypal account and add a new email address, then use that email address to make the purchase via app world. This always works for me, don't ask why. I have never been able to purchase apps in app world using one email address two times in a row.