Why does shift "r' not work to get uppercase R?

No matter what program I use, Chrome, Safari, Mail, FInder, Word, Messages, I can type the lowercase "r" but my computer won't allow me to do a shift + "r" to get an uppercase "R". I got to use cap locks. It is the only letter or punctuations on my keyboard that it does this for. I am running an Intel iMac from early 2009 and is updated with OS10.8 Any thoughts? -Jay