If you replced the bulb, I have to assume its an LCD, or DLP. Either way, it's probably the light block. I'm not sure how much you are willing to sink into it to get it repaired, but currently, a Sony SXRD light block is going for around 850 installed. LCD might be a bit cheaper. It probably wouldnl't hurt to have a shop take a look, and give you an esimate, but i'd expect the repair to cost nearly as much as a brand new Mitsu DLP, or even close to an entry level 60 inch LCD or Plasma.
Thanks, I read somewhere as well that perhaps it might be the blue filter. Is that a possibility do you think, or definitely the light block?