I cannot get the "a to b" looping video option to work

[Windmaker]

I don't know if I'm missing something, if it's a conflict with my operating system, or what the problem is, but I cannot get the (advanced control) option of selecting points a and b for continuous looping of a video clip. I have been clicking on the "a" at any given point during the video playback, and then clicking on the "b" button a little later in the playback, but it will not capture that portion of the video for continuous looping. Instead it just starts repeatedly playing a clip from near the beginning of the video that's only a fraction of a second or one to two frames long. I've tried selecting the buttons during normal speed playbacks, in slow motion playbacks, and even pause points, but nothing seems to work.

Can anyone tell me how to resolve this issue? I can't locate any info in the help section about this option.

[Sailor3333]

I have exactly the same situation in every respect described in Windmaker's posting. Using VLC 2.0.1 Twoflower w/ DirectX preference. WinXP, SP3 older PC.
Thanks for any advice.