A family of Microsoft relational database management systems designed for ease of use.
PhillJM,
First of all, what version of Project are you using? Second, is it updated with the latest Public update? Note, if you are using a subscription form of Project, it is updated automatically.
Have you set a status date? Is it earlier than the milestone date? If so, then indeed the milestone is a "future task" since the Status field uses the status date as a reference.
If the above is not your case, then please elaborate the scenario. For example, is the milestone linked to any tasks? A screen shot might be helpful.
Hope this helps
John