The reason for this is that Nullsoft has improved the decoding engine for better quality. So now it uses more recources and processing time.
If your mahine isn't fast enough, your glitches are the result.
If you want to have an old Winamp version, goto
http://members.xoom.com/Winamps
They have almost every Winamp-Version ever programmed.
Try Version 0.20 :-)
Digi