42in Vizio lcd tv loses picture and produces screech hum sound

A first glance, this lcd hdtv looks fine. It has a great picture and still does, but it has one, very annoying problem: After an hour of use, or more depending on the environment and circumstances, the tv will lose it's picture and produce a loud, frightning screech that can be heard outside of the house. When the tv enters this stage, the noise continues for about 7 seconds until the tv returns to standby mode. The Vizio logo remains white during this time also. After the tv enters into standby mode (orange lit logo), the only way to turn the tv off is to unplug the power cord, as the remote and tv buttons will not respond. Once done, the tv fires back up as normal, and has no loss of video quality -- almost as if nothing was wrong. TV Model: VW42FLHDTV10A (Vizio 42 inch lcd 1080p television) More useful information: At first I thought this was an overheating problem, as the tv was sitting in a corner, so I took the back off and placed the tv on my dining room table, where fresh air could easily reach the tv. The first time of doing this, the tv remained on for multiple hours without producing such an effect, but the tv in this case was left at the opening menu of Halo 2 (PC) when I had it hooked up to my computer. However, further attempts produced a result, but in two of the cases, no noise was heard but a small "op" and the tv seemed to carry out the routine process of going to standby after about 7 seconds. I have been able to reproduce this event a lot sooner by using an hair dryer to heat the back of the tv up (I managed to reproduce the event in about 15 minutes). One thing I have noticed, regardless of the hair dryer trick, is that the back of the tv (case opened) gets hot to the touch, but mainly concentrated in the left and right side of the tv. When I tried troubleshooting this, I found that the inverter board seemed hot to the touch, but due to my limited knowledge of lcd tvs, I did not know whether an inverter board could heat up like a graphics card. Also in a few cases I remember hearing a soft clicking noise coming from the power supply in the region where the coils are located. I have found this very tricky to troubleshoot, especially since the tv works fine for the majority of the time except for those instances. One of my theories is that there is a electrostatic build-up in the tv, and another is that the tv is over heating. The other theory is with a problem with the logic control board (not so bad) or the main board (hope not) due to the output of the noise being from the speakers. I'd like to point out that I tried looking for vibrating boards that might produce this sound, but it turns out that the speakers output this signal. I have already replaced both the inverter board and the power board, and the problem persists. There is a possibility with one of those replacement boards being defective, but I'm skeptical about that since the problem comes and goes, rather than something like the screen failing to turn on. I looked over the entire tv and have not seen any blown capacitators or burned transistors. Sorry for the lengthy description, but I feel that these details are neccesary. One thing to point out that, I have no intention of taking this to a repair shop. This tv is out of warranty and I'd rather not pay the $150 fee of just letting them look at it, let alone the parts and wait. I have a few questions to supplement this as well: 1. Which, all, components in an lcd tv can cause a hum/screech noise? 2. Are inverter boards supposed to produce heat like a graphics card? 3. What is a good method to further diagnosing whether a board is faulty, such as with a digital multi meter? Any other tips and information are greatly appreciated. Thanks!