Newly Installed Software Causes Outages in MIT's 411 Directory Services: Feb, 1998

• 
  Length of outage: Several outages, up to four weeks
  
  
• Number of people affected: Unknown. All MIT campus phone services affected

This older article chronicles the problems MIT was having with Bell Atlantic's 411 (directory assistance) services in 1997-1998. Apparently there had been a number of failures leading up to the major one in February, 1998.
Read the original article HERE.
Here's a statement from MIT's point of view:

"This was caused by a software change. Since the new software did not interface with ours, we had to reroute traffic," said Valerie L. Hartt, Supervisor of Operator Services in Information Systems.

It seems that Bell Atlantic would periodically perform upgrades on their own equipment which would render it incompatible with the calls they were receiving from MIT's system.

"Part of the problem with this was that Bell Atlantic never informed MIT's 5ESS service team that it would be performing this [upgrade] service ... Therefore, we could not inform the community, nor be available during the upgrade to perform our own testing."

For me, the funniest part of this outage is that fact that both Bell Atlantic and MIT were using identical telephone switches: The AT&T 5ESS, which is still in widespread use.