Animation is jerky, but slider is not

Question

When I do the following simple animation (from the book Mathematica Navigator, p. 316) the slider control changes the image smoothly, but when I play the animation it is jerky. Is there anything that can be done to make the animation smooth?

The code for the plot is as follows:

Manipulate[Plot[Cos[a x], {x, 0, 3 \[Pi]}], {a, 1, 10, 0.3}]

UPDATE: Changing the step value does not help; also, sometimes the animation stops completely, just gets stuck. Something appears to be seriously wrong with the animate function.

The main problem, the jerkiness, appears to be caused by Windows "User Account Control" (UAC) (see answer below). This "security" feature is present in Windows 7, 8 and Windows Vista. It can be avoided by either running Mathematica as Administrator or by turning off Windows UAC altogether.

Answer 1

Seems to be an artifact of high speed updating of the plot. On my system, V9.0.1 running on OS X, the animation becomes smooth when a has an increment of 0.2 or larger. That is

Manipulate[Plot[Cos[a x], {x, 0., 3. \[Pi]}],
  {a, 1., 10., 0.2}]

looks smooth on my system. I think this because the problem becomes more noticeable as the value of a increases, and further, reducing the update speed with the Slower button when the animation is running will smooth it out.

Answer 2

Perhaps generating the frames in advance would help create a smoother animation - but to my eyes there's not a huge difference - and there's a big wait at the beginning - it depends on what your use case is...

ListAnimate[
 Table[
  Plot[Cos[a x], {x, 0., 3. \[Pi]},
   PerformanceGoal -> "Quality",
   PlotRange -> {-1, 1}], {a, 1, 10, .01}]]

Answer 3

Further investigation showed this to be a problem when running Mathematica as a user under Windows 7. Under Windows XP and other environments the animation runs smoothly.

A workaround is to run Mathematica as Administrator on Windows 7 in which case there no UI pauses or animation pauses. Why running as an administrator makes a difference, I don't know.

Even running as administrator does not prevent the animation from stopping entirely at random points, but this appears to be from some different cause.