This sounds to me like the IF sensor did indeed choose that moment to die on you.
Did you try unplugging the unit for a minute and then restarting it, to totally give any lingering "smart" settings a chance to clear? Some players have "memory" like a PC does, and a badly programmed (or glitchy) software setting can mask as a hardware problem until you totally cold boot the player. I have no idea if your model is like that, though.
But if you want to treat it as a "software problem" for now, the next thing to do is see if the problem follows the disc: use it in another DVD player and see what happens. I would recommend you do NOT use a friends!
It sounds like you got it by mail-order, so there's no way to ask the store you bought it at to try it out for you. But maybe you can think of something.
Other than that, my advice is to treat this as hardware and contact Toshiba to ask for troubleshooting advice. Perhaps their website has a FAQ that will get you moving in the right direction.
Also, this thread may get better advice than mine in the hardware section.
Good luck!
