Quote Originally Posted by schoolboy View Post
@lat9... Error logs still occurring - but the checkout seems to be completing in spite of errors (they appear to be "Notices" more than "faults").

if you have a chance, FTP into the server and take a peek.
Those logs are due to the code-bug I introduced into the core when myDEBUG Backtrace was integrated. Check out this zen cart commit for the correction. It's nothing to do with OPC.