I have found a problem with DirectSound Output plugin (out_ds.dll) in case where HDD busy on heavy IO. I had no problems with playing mp3 files, only when playing vtx files (Vortex AY plugin).
First of all you need to open window with DirectSound settings:
"Winamp Preferences->Plug-ins->Output->Nullsoft DirectSound Output v2.49 (d) [out_d.dll]->Configure->Status".
There is demonstrating speed of buffer IO. So if HDD is busy on read/write operation, then "Buffer write cursor" speed slows down, so after several seconds (depending on buffers size) "Buffer playback cursor" run downs "Buffer write cursor" which envolve buffer cursors speed race which envolve sound choking and snapping.
I beleave this is rare issue, because mp3 playback plugin is optimized for that kind of behaviour, so basically have no that kind of problems.