I've asked around a few servers today. The ones that actually gave me information pretty much said the same thing. Starting last night, about 9-10pm CST, new players that joined in would start to *cough* in chat, with an added sound. This *cough* would also be sent to everyone in their Steam friend list. The issue was resolved at 5am CST. The cause is unknown, but it was not the work of a hacking player. So to the one that said that his keys were unbinded, that was an unfortunate coincidence of the time/
Also, when players left a DarkRP server with the *cough* bug, VAC would pick it up as a hack, and ban the players from any TTT, Prop Hunt, etc. servers that they joined. The owners of the servers are aware of the situation, so if you were banned, expect it to be resolved in a week's time.
I will post further information, but the active effects of this bug have been resolved.
Happy Roleplaying