If you're like me, you've made several different windows for your different chat channels.

And if you're like me you've moved some of the default channels out of the main window (I have guild, whisper, say, party, and raid in a second window).

2.4 has introduced an annoying bug that won't allow it to properly save your chat settings. I have to manually turn on and then off every channel that appears in the wrong window.

Blizzard is aware of the bug and there was supposed to be a fix yesterday but it was pulled at the last minute.

Here's an addon that will fix it until they get around to it.