After trying to debug a boffo customer problem for around 15 minutes today, I finally figured out the root cause of the problem. The problem itself causes me to laugh a little bit, now that I know all of the details.
One of the important certificates issued and used by ipsCA (who I'd never heard of before today) expired on 29-december-2009. It's one thing for a certificate that helps secure a single website to expire ; it is another thing entirely when a CA's certificate expires.
This blog posting is where I was alerted to this problem.
This is a spectacular failure. Wow.