Try unplugging and replugging your keyboard, and all the general stuff on the tech-support script (reboot word 2010, reboot computer, etc).
Should that not work, use another keyboard and see if the same problem happens. One of two things should happen;
1) Your new keyboard will function normally, showing you that it is a problem with your keyboard and not Word/Windows
2) Your new keyboard will not function normally, showing you that the problem lies within Word 2010 or Windows. If this happens, restore your Word settings to their default states (http://www.ehow.com/how_7257504_reset-word-its-default-settings.html
(I'm not sure how reliable this is)), or restore windows to an earlier time (http://www.sevenforums.com/tutorials/700-system-restore.html).