At first I thought I didn't suffer from the lyrics drift issue but further testing has proved that actually, I do. For some reason one album I've done is perfect but the rest exhibit this behaviour.

I tend to go through a track with 'click-as-you-sing' then I'll go back through it 3 or 4 times subtly adjusting it. I'd noticed that pausing or moving the time bar adjusted the timing so after changes I would save, start next track and then go back to the track I was synching. A lot of effort to end up with tracks where lyrics are still out of synch. I've tried different versions of Winamp on 3 different PCs now and hit the same problem each time. That's a good catch so I'll try some where I pause/adjust the track on each verse and see how that goes. My other option was to rebuild an old PC as a linux box and use XMMS.