Maybe this is obvious, but are you sure it isn't pasting in white text.
I've seen that happen sometimes in Word, especially if you are pasting from
an area with black background, white text, etc. It's caused me to say WTF
quite a few times. You can tell if that's what happens by clicking beneath
where the text was and then draginging up, highlighting text. If it appears
as black lines with white text, just use the button to the upper right to
change the color back.
-Will