I've got a GFCI receptacle and a regular receptacle powered respectively by two different circuit breakers from the same power panel. When the circuit breakers are switched on, both receptacles have 120 VAC at their outlets and read "Correct" on a circuit tester.

Now, when I plug my TV or anything else (which are turned off) into the regular receptacle, the GFCI receptacle trips and have at its outlets 0 VAC whereas the regular receptacle outlets have 72 VAC. Further, the circuit tester reads nothing at the GFCI receptacle (b/c it is now tripped) whereas it reads "Hot/Ground Reverse" at the regular receptacle.

Why is the regular receptacle affecting the GFCI receptacle when they are on different circuits? Does the "Hot/Ground Reverse" at the regular receptacle provide any clues?

Any help is greatly appreciated? Thank you!

You do not mention what caused this problem.
Did you change anywhere the wiring?
If so it seems that you are using at that socket a return from a different group, causing the unbalance tripping the switch.
;)

That reading is a classic "open neutral" situation.
You have lost a neutral connection somewhere. It could be in a receptacle or splice or back in the panel.
I'd vote for a bad backstab in a receptacle. Could be in a working one or a bad one.

I have to agree with the neutral problem, Start at the panel, follow the wires from those 2 breakers, and see where they exit panel, check the tightness of the Neutral that is with those 2 circuits. Do both circuits share neutral, and do you get 240 volts between both circuits, if you get zero volts between the 2, and 120 volts out from each, they may be on same phase and burned neutral open, could be in a box(recepticle, switch or light).
Was it working before, or is this after recent work.
Good Luck