Office 2010 has a new feature called Protected View. This protects you from potentially dangerous files downloaded from the Internet.
If you open a file in Office 2010 that was downloaded from the Internet, you’ll see something like the following warning at the top of the document (click to enlarge):
One of the effects of this protection is that it disables all macros and add-ins, including Felix. If you try to use Felix in this state, you’ll get the following error:
In order to use Felix with this file, you’ll have to click Enable Editing in the warning box, and then close and restart Word/Excel/PowerPoint. If you had other documents open, you’ll have to close them as well before Felix will work again.