Basically, what peter is saying is:
We can't help you unless you:
1) Provide full system specs (CPU, OS, soundcard, DirectX, etc etc)
2) Tell us what version of Winamp you're using (
2.78 +
update recommended)
3) What version of the ShoutCast DSP you're using (
latest recommended)
4) Whether you are using any extra 3rd-party Winamp plugins
5) Do you have the correct & latest drivers for soundcard?
6) Which Output plugin you are using (
updated versions of WaveOut/DS recommended)
FYI, this is NOT a Winamp bug.
This can be proved by searching the forums for "error killing decode thread"
and you'll find only 2 or 3 instances of this reported in the past 15 months.
(eg. this particular thread is from 15 months ago)
[edit]
booh, peter beat me to it