I need to store Visio files in vdx format for Subversion compatibility. When I ask Firefox to open a vsd file on the network, it appropriately states the file is a Visio file and asks if I want to save it. I select yes and the file opens in Visio. When I ask Firefox to open a vdx file in the same location on the network, it treats the file as a plain text file and opens it immediately--no option to Open With or to Save. I have tried resetting Firefox but it did not help. The application tab in settings does not show Visio file types in either instance. The underlying Windows 7 file association setting for both vsd and vdx is set to Visio.