[Phanx]

The problem is that in this code:

if not IsAddOnLoaded("Chatter") then
    self:RegisterEvent("ADDON_LOADED")
    self:Hide()
else
    self:ConditionalShow()
end

-- define a function so we dont have to paste the same code in the onevent box.
function self:ConditionalShow()
    if LibStub("AceAddon-3.0"):GetAddon("Chatter").db:GetCurrentProfile() == "MayronUI" then
        self:Show()
    else
        kgPanels:FetchFrame("chatB"):Show()
        Bazooka.db:SetProfile("MayronUI2")
        self:Hide()
    end
    -- Chatter is loaded here so we dont have to listen to ADDON_LOADED anymore, clean up this frame
    self:UnregisterEvent("ADDON_LOADED")
    self:SetScript("OnEvent", nil)
    self.ConditionalShow = nil
end

The "ConditionalShow" method is not yet defined when you try to call it in the first block. You need to define the method first, and then check for Chatter and call it. Just swap the order of the blocks:

-- define a function so we dont have to paste the same code in the onevent box.
function self:ConditionalShow()
    if LibStub("AceAddon-3.0"):GetAddon("Chatter").db:GetCurrentProfile() == "MayronUI" then
        self:Show()
    else
        kgPanels:FetchFrame("chatB"):Show()
        Bazooka.db:SetProfile("MayronUI2")
        self:Hide()
    end
    -- Chatter is loaded here so we dont have to listen to ADDON_LOADED anymore, clean up this frame
    self:UnregisterEvent("ADDON_LOADED")
    self:SetScript("OnEvent", nil)
    self.ConditionalShow = nil
end

if not IsAddOnLoaded("Chatter") then
    self:RegisterEvent("ADDON_LOADED")
    self:Hide()
else
    self:ConditionalShow()
end

Also, (mainly directed at ravagernl) don't mix single- and double-quotes for defining strings. Pick one style and stick with it. I'd suggest double-quotes, since you'll want apostrophes in your strings more often than you'll want quotation marks, but either one is fine. Just don't use one on one line, and the other on the next line. It's like mixing tabs and spaces for indentation in the same file.