Followup British Telecom outage reason

BT is telling ISPs the reason for the multi-hour outage was a software bug in the interface cards used in BT's core network. BT installed a new version of the software. When that didn't fix the problem, they fell back to a previous version of the software. BT didn't identify the vendor, but BT is identified as a "Cisco Powered Network(tm)." Non-BT folks believe the problem was with GSR interface cards. I can't independently confirm it.