Originally Posted by Horsedick
I'd try this but I'm sure they will release an update tomorrow or sometime this weekend.
No.... This is the new format....
We apologize for the lack of warning regarding the SteamID format change in today's update. It was our intent to give the community a heads-up before the change was released, but it was missed.
The change was made to update TF2 to use the current SteamID format, which most other games on Steam and Steam itself uses. You will find that you can now use SteamIDs rendered by these other locations in your interactions with the engine. The engine will still recognize the old format, though, so your current server ban lists should still be valid.
The conversion equation has already been posted by a community member, but here it is again:
Example: STEAM_0:1:1234 ---> [U:1:2469]
We're sorry for the problems this may cause while you update your scripts to use the new format. It was not our intent to disrupt your servers.