I have no idea why COMMAND + C doesn't always register from the first time. I sometimes try to copy something off Word, but I have to press COMMAND + C more than once for it to register, otherwise COMMAND + C just prints what was copied in clipboard before. This becomes very irritating.
However I realised that if I press COMMAND then pause for a second, THEN press C, the command always registers.
EDIT
I noticed that when I select any text in word, it takes about a second for the Cut and Copy buttons to be highlighted (otherwise they're greyed out). And THIS has direct effect on this problem. Only when they are not greyed out anymore can I copy and paste using keyboard shortcuts correctly.
What is happening ?