That's a daily occurrence with me! My keyboard undoes the "lock" anytime I restart the computer, so I have to lock it again. It is very frustrating. If anyone knows how to make it remain locked, please share! I have a Microsoft Wireless Natural Multimedia Keyboard, but I think just about all of my Microsoft keyboards have done this.
You would think after 9 years of dealing with this I would remember, but no, I am reminded by trial and error every day that I have not hit the Lock key!