Error: "You cannot write to channels until you become level 73."

Hi.

So I apparently can no longer talk in channels on my lvl 69 bank alt, thus rendering said bank alt nearly useless. The problem is that, since yesterday, I keep getting this irritating error whenever I try to talk in any public channel that says "You cannot write to channels until you become level 73." A few days ago and ever before, I was able to talk in channels, and I had my brother test it as well, and he said that he is able to talk in channels on his lvl 60 Tauren Druid, so what gives??? I've already checked to see if it was some addon malfunction, and it doesn't appear to be. I'd appreciate if someone could help me troubleshoot this.

Is no one playing a character lvl 20-72 that is having this problem? Is it just me?

Okay. Two weeks have gone by and I'm still having the same problem. I made an in-game ticket but it hasn't been answered yet and I haven't been able to use my bank alt for two weeks, so if anyone has any suggestions, I'd be grateful. I've already had a few other people test this for me, including my brother and some random strangers, and I am the only one I've found so far that cannot write to channels before level 73. I've tried disabling all of my addons and resetting my WTF and Cache folders. I've also tried logging in from another computer (my brother's computer) and although he can speak on his lower-than-73 characters on his accounts on his computer, I cannot speak on my lower-than-73 characters on my accounts on his computer. I have two accounts with characters between 20-72 and both of them are having this same issue. I am now led to believe that this must be a bug with my accounts, for whatever reason, because it obviously is not my WoW folder nor my computer.

This happens with my DK (who is currently sitting at 65) right now, but none of my other characters. I assumed that it had something to do with DKs starting at 55, but apparently not. Quite a weird issue. I have no idea how to resolve it though. =\