Sounds like either a connection fried, a component burned out, a power supply failed - could cost from about $75-100 if a simple connection gone bad to more than the TV is worth if a major board or component failure. A TV Repairman minimum charge to even diagnose it is likely to be about $75-100.
Unfortunately, if you look at the reviews on Amazon for this model here -
there are several comments identical to your POP description. Google this search phrase to see more complaints about Z-board failures and blown fuses - Toshiba 42HP66 failure complaints . Sounds like getting Toshiba to recognize a systemic failure mode is a lost cause, from the comments. Repair cost eveindently about $600-700, and appears to happen again in a year or two, so evidently they are using the same parts to repair them, not corrected designs.
Though you probably paid $1400 or so 7 years ago,, similar TV's cost about $400-500 today, so my recommendation, based on the comments and personal experience with modern electronics components failures, is to buy a new one.
IF it sparked or put out smoke, you could be a Consumer Product Safety Commission safety complaint on it, and when Toshiba contacts you in about 2 weeks they might do a replacement to keep the government off their back - if you can live without the TV for a month or so.