Unable to complete fax transmissions

I have recently applied the firmware fix that addresses the fax line answering during an ongoing phone call. After applying that firmware, I am having difficulty completing fax transmissions to pretty much any fax number expect (isn't this typical) Canon technical support. I've tried to send to one of the free internet fax receipt services, my FSA provider, my corporate office, and doctor's office and while the machine connects, negotiates and appears to start sending information, it terminates after 15-50 seconds with a "NG" code (no good - isn't that especially helpful).

Any one else seeing similar issues? I asked Canon to provide the original firmware and they've refused. Also, I've while the number of occurrences of the fax answering during an ongoing call has dropped significantly - its still not completely eliminated.