I think I can shed some light on this topic...
My wife's visa was approved on May 26th. We expected a call from the embassy the next day for us to come pick up her passport and visa. Three days later, nothing. I gave them a call, and they told me that the processing center is experiencing technical difficulties, and they don't know when it will be back online.
The visa is approved, we have the alien registration number, but the visa simply cannot be printed. We are suppose to fly in two weeks so I asked them what to do. Wait and hope they get it back online was the response.
Supposedly it's a worldwide outage effecting all embassies and consulates. The same thing happened last July, but I haven't found any recent news about it so I was searching here.
The only notice of the problem is on the CEAC website. If you visit the CEAC website and click on the D260 form link, a notice about the problem appears at the top of the page in red.
Good luck to us all.
Edit:
Here is the notice from the CEAC website:
"We are aware that some applicants continue to experience technical difficulty. If you are unable to access the form DS-260, DS-261, or pay immigrant visa processing fees and have an emergency need, please contact the Embassy where your visa will be processed for further instructions. We are working to address this issue and apologize for any inconvenience."
Prague got a reaction from Amhara in K-1 Visa approved! No further updates??