[zork]

Maybe http://wowpedia.org/API_Slider_SetStepsPerPage, http://wowpedia.org/API_Slider_GetStepsPerPage causes a sort of endless loop? That are the only changes since 5.4 for slider object.

Getting an endless loop is easy. You set a value and on value set you call a function that sets a value. O_O

What will this do for you?

--If steps >= 1, the Slider's value will be changed by 
--exactly Slider:GetValueStep()*math.floor(steps) in the 
--direction of the click.
slider:SetStepsPerPage(0) --disable SetStepsPerPage
 
--[[
slider.SetStepsPerPage = function(...) 
  print(self:GetName().." called SetStepsPerPage")
  print(...)
end
 
slider.GetStepsPerPage = function(...) 
  print(self:GetName().." called GetStepsPerPage")
  print(...)
end
]]--

If your valuestep is very low (0.001 or lower) make sure to use bigger steps like: 1/valueStep