Good chance you have a convergence circuit failure, which is very common on a projection this age. The parts are about 60 bucks, chips and fuses. The hard part is getting someone to fix it for under $250 labor - it is just an awful tv to work on difficulty-wise. I would go after this repair as long as you have no other issues with the set.
I have the same problem with my toshiba. The thing is i do not know if there are any other issues with the TV. Could it be the picture tube also