Even though the file shows as greyed out when using the Open option, I opened the file by drag & drop onto the program icon in dock via 2 versions of Word, TextEdit & Tex-Edit Plus; all were able to open the file. I guess you could make a copy of it & try changing extension to .doc or .txt & see if that helps. Else in your Text programs, when choosing open, click option for "all documents". An m3u file is just a text type of file, it simply contains information that points the audio player to where to find the song file to open it.