Windows 7: HDMI half-works, then gone entirely on new build

Hello,
I built a system today with these specs:
　
Mobo: MSI 785GM-E65 (AMD 785G chipset)
GPU: (Integrated) Radeon HD 4200
CPU: Phenom II X2 550 Black 3.1ghz w/ Stock Heatsink-Fan
RAM: 6GB DDR3 1333 PC10600, Crucial Micron
Case: MicroATX w/ Antec 550W ATX PSU & 80mm Fan & 60mm Fan
OS: Windows 7 Professional x64
HDD: Western Digital 80GB ATA100/IDE
Peripherals: GIGABYTE AirCruiser G PCI Adapter, ASUS Internal CD-RW, Samsung External DVD-RW, PS/2 Keyboard, USB Mouse
Monitor: Westinghouse 19" HDTV #SK-19H210S
　
To summarize, my first problem was HDMI video- and audio- output instability(read below for description) -- but this has been superceded by a new second problem-- not getting any HDMI output at all!
　
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As soon as I completed the build, I connected my chip's HDMI-out to my HDTV. The system POST'd successfully to HDMI video out and I was able to install Windows without a hitch.
　
From the start, there was video instability. The display would go black for an instant and immediately re-appear. HDMI audio crackled on any UAC (User Account Contol) prompts and any fullscreen events like maximizing/minimizing from a fullscreen app/game. (The crackle was only for a split second and sounded like the noise you might get from any speaker if you yanked the audio input source out when it was on higher volume.) The display black-outs improved upon driver updates(though I only used the system for an hour or so, so possibly not sufficient sample to be representative). The audio crackling on UAC/fullscreen events remained.
　
Apart from the crackling noises on UAC and fullscreen events, audio sounded fine. It played any of the Sample Music tracks included with Win 7 great and clear...
　
To troubleshoot the video/audio issues, I swapped the HDMI cable connection for a VGA cable and Speaker analog cable. This worked perfect--no issues. So the video card and sound controller seemed to be functional--it was an HDMI port issue...
　
I swapped the VGA cable and Speaker analog cable back to HDMI ... and the HDMI video output would no longer work. Stranger still, HDMI video output will not even appear for the POST, let alone Windows 7.
　
I have since uninstalled and reinstalled the OEM disc drivers, the AMD-ATI website's latest drivers, the MSI(chipset manuf.) website's latest drivers ... no dice. I have booted and played with all combinations of HDMI/VGA cable sequences(leaving both plugged, HDMI plugged while booting and changing later, just lots of weird stuff that didn't accomplish anything).
　
The HDMI cable and HDTV work. I can successfully connect my laptop's HDMI out(Nv9300GS card) to the HDTV and display fine.
　
I have connected my VGA to an old CRT monitor(works), and the HDMI to the same HDTV. The VGA/CRT display works. The HDTV display does not appear whatsoever in any Control Property->Display dialog boxes, and the ATI HDMI Audio Controller device is "unplugged" in the Select Audio Output dialog ...
　
I have now formatted and re-installed Windows 7 with this same VGA->CRT monitor and HDMI->HDTV multiple displays setup... and it still only detects and uses the VGA->CRT monitor.
　
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Please advise... how I may troubleshoot and resolve these problems. I would like to get HDMI working on this system again, and also resolve the audio crackling issue.
　

Hi.

Install the latest driver from ATI's site. See if there are any bios updates. Disable any cpu throttling in the bios, to test. Do a Windows Update.