I use the Mendeley plug-in for Word. Is this what you mean? I don't believe Word has a built in citation manager. I've found that you need to be careful in looking at what options are selected that the citation style you want is actually the one selected. Also, Mendeley and other web or text-crawler based reference software doesn't always collect all the details correctly or assign a source to the correct category (eg it might read a paper or book chapter as a webpage depending on how you access it, which would then read differently int he citations).
