I found the problem. Intuit had posted (perhaps for an earlier version of QB) that the final ENDTRNS should be followed by a tab (even for comma-delimited), or the final invoice would not be imported. This seems to be the problem at this point. If a tab is included after the final ENNDTRNS, no transactions are imported at all, yet a 'Successful' message is displayed. Removing the tab seemed to do the trick - it works fine now.

Thanks for your help.

David