We had a HUGE downtime - we are talking 50 hospitals (not known for being able to necessarily have the most up to date everything) on downtime procedures because the cert company changed their name and when the SSL cert was loaded onto one of the LDAP machines, anything using LDAP that didn't have the new root cert (anything out of windows support and probably even some of the newer stuff) just went boom. We updated the root cert for the software I support after a lot of help from the vendor since it's not something typically done, just to undo it when it was impossible for some of the older stuff to update.
We were up all night when one high level guy just said F it and bought a new cert on a company credit card from a well known company. They gave us no trouble, it was instant and it just worked. We are now going to be canceling and moving our contracts by the guys who decided to change their name on all their certs and refused to give us ones under the old name. The original vendor was awful and we just had some Indian saying he couldn't do anything, so the C level was like - fine, you can't do anything, we will.