Maybe you should mention what kind of client you’re using to listen?
If you’re listening with WinAmp as it seems, you probably should ask if WinAmp supports those… hmmm… or actually not, since it seems to be part of the standard:
ID3v1 tags are at the very end of the file (have to be), while ID3v2 tags usually are at the beginning (they can be in different places, but nearly every tagger stores them at the beginning). So if you’ve only got ID3v1 tags and stream (playing live instead of downloading then playing), that means the ID3v1 tag will arrive when the song is finished playing…