... first of all, it's not a problem. That is by design.
When you copy something in Word to the clipboard, there are many hidden characters used for formatting. Pasting the contents of the clipboard directly into a smart application such as Excel will take all of those hidden characters with it and if it can not do so, it will paste as a bitmap (BMP). It's been that way for a long time. If you only want to 'grab' the text and not all of the formatting that goes with it, you always have to run it through a simple text editor such as Notepad first.