Jerky playback

[TT]

For some reason, playing back many videos, regardless of format, with mplayer 31878 causes a slight jerky hesitation with my WinXp P4 computer. About every 4-seconds there's a slight (tenth-second or so) pause, then a quick speedup where the vid catches up. There's no pause with the audio. Mplayer 30521 works flawlessly, but builds after that exhibit the problem. I even tried dropping the vid directly in mplayer (bypassing smplayer entirely) with the same results. So it's mplayer that's causing the problem. Is this a known problem with mplayer, or is there a way I can 'fix' it through smplayer? I tried different cache settings - same result. Thanks.