Vista - Cursor Positioning and Copy-Paste Deactivated in Word

On January 8 in Word (Office Enterprise) I was able to move my cursor within
the text using my mouse and left click, as well as click-drag to highlight
text to copy and paste. On January 9 it no longer worked. The Copy-Paste
icons top left in the toolbar were grayed-out (deactivated). I have to move
the cursor using the arrow buttons, and cannot copy and paste. Why?
As an aside, the mouse moves the cursor just fine, slides the page up and
down, and works with all the other menu items. Likewise, I can go into Excel
and Powerpoint and use the mouse to place the cursor within text. So, it only
does not work in Word. I went to Control Panel, removed the software, and
re-loaded it and the problem remains. Any ideas?