Chat window problems.

So, this is an odd one. Occasionally, when I start the game and go to type in chat, everything works. Most often, when I start the game and go to type in chat, everything BUT lower-case m keystrokes appear. When this happens, I have to type words that have an m in them as a capital. (e.g. "SoMeone - Me - Might find theMselves coMposing sentences like this.")

Obviously, my keyboard works. I even have "m" bound to bring up/close my companions window - which it does. However, the chat window just likes to "eat" lower-case m keystrokes. The chat window acts like I did not even hit the key. I'm at a complete loss here as to what the problem could be.

Help?