If you would've read the original post, he swapped the entire lid to another laptop and it works, so that proves his LCD, cable, inverter, and blacklight tube are all good.
And yes, the +5 is a certain pin on the cable. Just look at the inverter, it should only have 4-6 wires going to it, and looking at the traces, it's easy to tell what does what. Usually the +5 pins on the inverter lead to a small surface mount fuse before going to the chopper. The grounds are pretty obvious. And 1 or 2 pins will have a very small trace that usually leads to the PWM/Oscillator IC, those are the logic turn-on signal line(s).
I agree, the 5 volts should certainly be on the cable attaching to the inverter board. But.... the cable to the board is a flat ribbon with 24 conductors. (the inverter also has 7 LED's for power, charge, wireless, sleep, caps, num and disk). I have a schematic for the T41 but it doesn't include the display circuitry.
Probably should just junk the thing but... I'M STUBBORN!! :-)