I've just submitted v2.0.4 of OPC to the Zen Cart Plugins for review and will post back here once it's available for download.

This release contains changes associated with the following GitHub issues:

#143: "Suburb" and "Company" changes not saved on address update.
#144: Maximum address-book entries not honored for account-holders.
#145: Downloads result in a 0-byte file.
#146: Guest-customer can't download from the "checkout_success" page.
#147: Payments can't be made with methods that "collectCardDataOnSite".