The full instructions for your remote are are below (provided that you have our standard remote that has only two buttons at the top for TV and STB)
http://www22.verizon.com/cs/groups/public/documents/onecmsresource/p265usermanualmarch_e48a.pdf
You want to follow the directions for key fix. That tells you to press and hold the OK button and the asterisk button ( * ) . Then let them both go. Press and hold the mute button until it mutes your television. When it mutes it, quickly let go. Press OK button to save it.
I had the exact same issue and your advice worked perfectly for me. Thank you!