It sounds as if you may have saved a file in your Max search path with the name "button." This is the most common reason for objects to be greyed out. Do a search for "button" on your computer. You should have the actual Max object called button.mxo (Mac) or button.mxe (windows), but make sure you don’t have a file named something like "button.maxpat" or "button.png" located in the search path where Max can find it.