Blank Page error

We started a similar thread here before the most recent Marketpress upgrade (v 2.2.1), however we were only getting the error when someone inserted an invalid zip code:

We are using Paypal Express + Digital Products only. We have verified there are no other Payment Modules currently active.

We've since upgraded to v2.2.1 and are now getting this blank page on every order. Basically once a user clicks "checkout now" after the cart they goto the blank page (see attached screen shot).

We're planning on launching tomorrow and really need to get this bug fixed, is there anyway we can get this working until the bug is fixed in the next version?