I have the 52 inch model and had the same probem. I bought my television through Best Buy, and ended up getting replacement bulbs in 7-10 days from both Best Buy and Toshiba. Then, a few days later, we received a letter from Toshiba stating that there had been many problems with the bulbs in these televisions, that they had developed a better, more reliable bulb, and would be sending these out very soon. We have not received it yet, but expect yet another replacement bulb any time. In short, we have a new bulb, a replacement for that one, and yet another replacement on the way. That should cover us for at least a good while.
I have read quite a bit online about this issue, and the consensus seems to be that the bulbs that come with the televisions are generally duds, but that the replacement bulbs appear to be working fine. It is annoying, but I am hopeful that the problem is now fixed, and that the newer bulbs will last a good long time before being replaced.
I recommend that you contact Toshiba directly for more information and a replacement bulb. Good luck.