I'm always up for a good conspiracy theory. LOL
A conspiracy theory making the rounds speculates Microsoft may have changed the system diagnostics test to report Red Ring of Death error as E74 instead to save money. For errors reported as E74, it would force customers to pay $100 for the repair if the error occurs later than 12 months after purchase. The E74 error is not covered under the 3-year extended warranty set in place for the Red Ring of Death malfunction.
Joystiq points out that this theory is unlikely because survey respondents are still reporting Red Ring of Death errors after the launch of the New Xbox Experience.
I have only used my xbox 3 or 4 times since the update so I hope its not related