Both group chat and IM failing to initiate. I mostly experience it in Firestorm Social Island (simhost-0be97bd680c67540a.agni), as do the rest of the team.
Starting an IM with someone else will work most of the time and every once in a while end up with a popup stating "Unable to start a new chat session with Username. The session initialization is timed out".
Group chats will either fail silently or give the following message inline:
"Second Life: You are the only participant in this IM session. Your message is not being broadcast at this ti2me."
Tested on Second Life Release 26.1.1.23806384790, Alchemy Beta 7.1.9.2516 and Firestorm 7.2.3.80036.