Every once in a while, I find that Microsoft Word seems to think that Caps Lock is on, and everything I type appears in UPPERCASE. Other Windows applications and the light on the keyboard show that Caps Lock is actually off. Closing Word and opening the document again does not fix the problem.
This finally annoyed me enough that I did some research and found http://www.techsupportforum.com/microsoft-support/microsoft-office-support/70154-ms-word-auto-caps-lock.html. Apparently when this happens, I’ve accidentally hit CTRL-SHFT-A (or maybe CTRL-ALT-A depending on the version of Word?). This enables the font style All Caps. I probably meant to hit CTRL-A (Select All), and if I accidentally hit CTRL-A before CTRL-SHFT-A, my entire document is suddenly UPPERCASE. Selecting the text and pressing CTRL-SHFT-A again fixes it by turning All Caps off. Or select the text in All Caps and click the Clear Formatting command, which is top-right in the Font group on the Home tab (the image shows the characters “Aa” with something that might be an eraser). Unlike the Caps Lock key, which applies to all keystrokes, font styles apply to the text for which the style is enabled, which remains after closing the document.
In any case (pun intended), maybe someone else will find this information useful.