WowAce

It starts mainly when I'm in a dungeon or raid. It doesn't stop until I reload after the dungeon or raid.

419334x ...aceShadowedUnitFrames/modules/indicators.lua:180: bad argument #1 to 'SetAlpha' (Usage: self:SetAlpha(alpha))
[string "=[C]"]: in function `SetAlpha'
[string "@ShadowedUnitFrames/modules/indicators.lua"]:180: in function <...aceShadowedUnitFrames/modules/indicators.lua:174>

Locals:
(*temporary) = Texture {
enabled = true
status = "ready"
0 = <userdata>
}
(*temporary) = -0.000000

wotlk 3.4.1.47720

The problem here is that the remaining time subtraction on line 179 of modules/indicators.lua occasionally goes negative and passing a negative value to SetAlpha produces the error, this fix is to change

f.fadeList[fadeFrame] = timeLeft - elapsed

to

f.fadeList[fadeFrame] = math.max(0, timeLeft - elapsed)

I can confirm this bug.