There are clearly major problems here. FlyingDentist's report is consistent with other accounts of success using old DC numbers, but even that doesn't seem to be a guarantee.

The worrying development for me is that even Joanna's interventions no longer seem to work. As well as four segments missing from March, my wife and I still have unposted miles for CO flights from November (two segments from an itinerary, the other two flights posted automatically). I've tried everything: (1) letter with BPs clearly showing BD*G and DC number; (2) mail to Joanna with BP scans (reply: passed to admin, miles will post shortly); (3) another letter with copy of BPs; (4) another mail to Joanna (reply: sorry, passed to admin, miles really will credit shortly) and am now waiting for a reply to (5) another mail to poor Joanna.

These weren't long flights, but they still add up to over 4,000 membership miles that we'll probably be needing come November (if DC still exists come November).