It can be very difficult to find accomodation in that part of the world during holiday season (Easter 10th-13 April, 2009).
is held over Easter so I would not be surprised to find that most of the better accomodation is booked.
I don't know your budget
but your options include :-
1) Book with a name brand accomodation chain.
2) Buy or bring a cheap
lightweight tent and camping basics.
3) Rent a campervan in Brissie. I see a lot of Maui
on the road.
My experience of being in that area during holidays is that camping (or campervans) is the superior option. There are many good grounds and more will probably be made available, some in really nice places.
The Bluesfest website has information on camping (tent) options. A Google
search on "Byron Bay camping" will give more information.