When I highlight hyperlinks in Word, the highlighted part disappears the next day(the words remain). help!?

I have no idea what's going on, but it keeps happening. I'm taking quite a bit of notes for a paper I'm writing in Word, so I've created a bibliography and have highlighted the books I have finished working on. When I save the doc. and open it again the next day, the highlighting (but not the words) disappear! It only happens to the highlighted words which I have made into a link (I also link some book titles to the corresponding notes a few pages down). The highlighting which was not made into a link remains ok. I have no idea why this is happening. Is there a way to fix it w/out getting rid of the hyperlink? thanks