The issue is on valve's side. They updated their interface but didn't update the client.dll file associated with HL2DM or DOD:S from what I've read.
Found this on the steam forums. I've got the same issue.
Just need to wait now for them to put an update out.
Was playing in the de_dust2 24/7 server earlier today and a player named "New day new nick" was using a blatent aimbot that everyone saw. He was kicked but I assume it would be preferred that he would be banned - grabbed his id before he was removed.
steam_0:1:31884763