Not on that page, cause I set the $roster->output['show_menu'] to only show account_menu. But on a page where it's set to show all menus the output is:

My Account|Displays your characters, guilds, and realms.News|Post articles and other items of interestSearch|Search items and recipes in the databaseCredits|Who made WoW RosterRoster CP|Roster Configuration PanelGuildBank|Shows the inventory of characters marked as the Guild BankGuild Info|Shows Guild Info text from WoWInstance Keys|Lists Azeroth Dungeon keys for guild membersProfessions|Display a List of professions for all membersPvP Stats|Shows PvP Log stats for this guildMembers|Displays the guild member list with player notes, last online time, etc...Stats|Displays each guild member's stats such as intellect, stamina, etc...Honor|Displays each guild member's pvp informationMember Log|Displays the upload log for new members and removed membersQuest List|Search for quests other guild members are onMembers|Displays the member list for all guilds on the realmGuilds|Displays a list of all guilds on the realmRegisterTogin|Displays the login|lost password page.My Characters|Displays your characters.My Guilds|Displays your guilds.My Realms|Displays your realms.

I dunno at this point
I would double check your locale files and maybe even all your locale files and see if this locale key appears elsewhere

LOL... Oops, I had another $lang['account_register'] and I have an array of messages that uses $lang['account_user']... So it was my miscoding all along... I just added _bttn on the two locale strings and changed the button names in install.lib.php and now it works fine. Thank you for your troubleshooting though!

No problem
I've done this kind of thing before