Since 4.1, a weird flicker behavior seems to happen when a scale animation reaches its peak. Here's some example code for my test case:

local f = CreateFrame('Frame', nil, UIParent)
f:SetSize(64, 64)
f:SetPoint('CENTER')

local t = f:CreateTexture(nil, 'OVERLAY')
t:SetTexture([[Interface\Icons\INV_Misc_EngGizmos_17]])
t:SetAllPoints(f)

local g = f:CreateAnimationGroup()
g:SetLooping('BOUNCE')

--animation = AnimationGroup:CreateAnimation("animationType" [, "name" [, "inheritsFrom"]])
local grow = g:CreateAnimation('Scale')
grow:SetScale(3, 3)
grow:SetOrigin('CENTER', 0, 0)
grow:SetDuration(3)
grow:SetOrder(0)

g:Play()
Edited by Tuller on 4/30/2011 12:54 PM PDT