Help with Megascenery

I bought Megascenery MidAtlantic. I installed it in FS9. It worked fine. After I flew it a couple of times, I wanted to see what it looked like without it. I choose my favorite midAtlantic airport Ronald Reagan Washington National (KDCA), and chose change and hit add-on. The Megascenery blocks came up where you can select or unselect an area for display. I unchecked them, and flew a couple of missions. Now when I call up KDCA and check the search add-on scenery block, I get all blanks in the add on scenery option. I no longer get the Megascenery option blocks where you can check a scenery segment on or off. Is the answer to reinstall the program by reinserting the Megascenery disc and doing another install.BillC9