Thanks to Rob for posting the patch for Firefox 4.

This package is now updated to support osC 2.3.1.

Please note that support for the One Page Checkout is removed. The OPC contrib is changing to fast to keep track of it and there seem to be a number of versions and fixes in circulation. If you use OPC and have trouble integrating postcode lookup, get in touch - we will try to get your setup working.

More...