Posted this on the official forums a while back.
If you're not a death knight and you call this function it'll crash the client.
Work around I use in my mod
Code:
local GetRuneCooldown1 = GetRuneCooldown
local function GetRuneCooldown(RuneIndex)
if Main.PlayerClass ~= 'DEATHKNIGHT' then
return 0, 0, true
else
return GetRuneCooldown1(RuneIndex)
end
end