Festivals in PNG May - June 2008

Hello,

We are travelling to PNG next year (2008). We want to plan our trip so we can visit a festival in the month of May or early June.
We read about TUMBUNA SINGSING , THE PNG COFFEE FESTIVAL and MILAMALA YAM FESTIVAL.
We would like to find out when these festivals are taking place in 2008. We tried to contact the PNG tourism board, but we got no reply.
Hotels in the festival areas are not too helpful either. We need this info in order to be able to buy the necessary plane tickets.
Can anyone help us ???? Has anyone been to one of these festivals ???

Thanks a lot,
Cheers,
Volkske.