Problems with PayPal on MarketPress

At this point, we have chosen to use PayPal Express Checkout (now set to live) on our site.

Here is what's happening when a customer goes through a check out:

1.After filling out the shipping address and clicking on "Continue Checkout",
a customer is redirected to PayPal where he can select the method of payment and click on "Continue"
2. Redirect to "Confirm you purchase" page BUT
a) the page does not have any previously entered shipping information
b) At thew bottom of the page is the following message: "Whoops, looks like you skipped a step! Please go back and try again."
3. If a customer clicks on this :go back" link, he is redirected to "Payment information" page, which is obviously empty since PayPal is a method of payment

- If a customer chooses to click on "Continue" , he is redirected back to shipping info page, and the circle continues.

Can you point out why this is happening and how to correct this issue.

Thank you!