Not asking for help, just adding to our knowledge base since we're a well indexed website/database in Google and I was doing some hair-pulling over the past few weeks looking for some answers as SPECIFIC as this.

Also, in the event that any DP members have this problem, here's a decent troubleshooting solution:

I recently had problems with my 55 inch Bravia purchased in 2009 dropping HDMI signal intermittently.

I had recently updated to the latest firmware (with all HDMI cables still attached) and I noticed that suddenly thereafter HDMI signal/handshake would intermittently begin dropping both audio and video in the middle of doing anything (Cable Box via HDMI, PS3 via HDMI, XBOX 360 via HDMI, Blu-Ray Player via HDMI) and quickly re-connecting (usually about a 5 second drop).

As I had originally outfitted all of my hardware with $2 no-brand HDMI cables I suspected that there was perhaps some type of manufacturing problem with one of the HDMI's that was causing some ground or short problem on the HDMI controller.

So, I went out and purchased 4 HDMI 1.4 standard cables with ethernet to ensure that I was getting the best, cleanest connection. (Yes yes, I know that HDMI are digital connection and not like analog A/V cables, but a defective HDMI could easily cause handshake dropouts, and I wasn't sure if the new Bravia firmware liked 1.3 or 1.4 standard cables "better" *shrug*).

That by itself didn't solve the problem, so here is what I did that did solve it for me. I'm not sure exactly WHAT fixed the problem but one of the below corrective measures did it. I suggest trying them all.

a.) re-flashed the latest firmware (unlike other devices it lets you re-flash the latest version again if you need to) but this time with all TV connections UNPLUGGED. No HDMI, no A/V, no Components.

b.) unplugged my TV for a minute and pressed the power button while it was unplugged to attempt to discharge anything left in the capacitors.

c.) unplugged all of my HDMI devices for a few minutes and pressed their respective power buttons to attempt discharge them.

d.) reset the Bravia to "factory settings" by holding the UP Arrow on the remote control and pressing the power button on the side of the TV (it took two presses to reset and power down, but when I powered up it was factory fresh asking for language, date/time etc.).

Then I re-connected all my HDMI devices and did the following...

e.) Turned OFF "HDMI Control" on the TV settings (the setting that lets HDMI devices control automatically power on/off & switch-over to the HDMI device that was most recently powered on) - I suspect that THIS was the cause of the problem, but the earlier instructions above can't hurt anything.

f.) Managed the HDMI inputs and turned OFF the "auto" option for each one (which I believe is similar to the HDMI Control setting). I also custom labeled all my HDMI inputs while I was in there for good measure.

So, about a week in from doing the above and I have NOT experienced any drop-out of audio or video!

I recommend everything above if you're having issues with a Bravia going black for 5 seconds or so every 10-20 minutes, with the key things being - a firmware update with NO CABLES ATTACHED, an un-plug to reset the HDMI controller on the TV, a factory reset to clear out any potential setting software errors, and most importantly TURNING OFF the HDMI CONTROL settings & turning the "AUTO" option off for each individual HDMI port.

Best of luck!!!