Does it still exhibit that ridiculous "protection" where it requires you to press it for half a second or so before it activates? It drives me mad, I have to press it two or three times before I remember where I'm typing and hold it down for the ages it requires.
OS X has no such feature. Some particular keyboards have built-in protection against accidental CAPS LOCK, though, so that may be what you are seeing.
If you are using an Apple keyboard and it has that behavior, check for a firmware update. They issued an update a long time ago that turns off that behavior on that key when it is being used for something other than CAPS LOCK.
