Sony KDL-32M4000 SD/HD channel changing glitches (popping, flashing, signal loss)

I just purchased a Sony KDL-32M4000, and it's all good except for changing channels from HD to SD and vice versa when connected via HDMI to either a Motorola DCT-6416 or DCH-3416 DVR provided by Cox. The issues are these:

1. The HD/SD and SD/HD channel transitions take 5-10 seconds each. The DVR channel banner will rapidly flash on and off five times before the channel appears, and about half the time, the entire display will flash as many times between green and black. The lengthiest transitions consist of several seconds of flashing, momentary display of the channel, a few seconds of signal loss, until finally the tuner locks on for good. By contrast, my NEC 20WMGX2 monitor, connected to the same DVR via HDMI/DVI, takes no more than two seconds to switch between the same channels, there is exactly one banner flash, there is no green screen flashing, and it never acquires/loses/acquires the signal; it gets it right the first time, every time.
   
   
2. Much worse, the transition on the Sony is accompanied by a loud pop from the speakers. I'm talking about wincing in anticipation of the pop and then flinching anyway loud. Pressing mute takes it out completely, but otherwise changing the volume has no effect on its loudness.

I spent a couple of hours on the phone with both Sony and Cox, and each ended up pointing the finger at the other. So I returned the TV to Best Buy, and they were happy to exchange it for another of the same model. It does exactly the same thing as the first.

Before calling anyone, to troubleshoot, I tried different HDMI cables. I tried the two different models of DVRs given above, the Motorola DCT-6416 and DCH-3416. I tried both HDMI ports. I verified it doesn't occur when switching inputs between a DVD player connected via HDMI and an SD channel on the DVR; the DVD player is flawless, in fact. Nor does it occur over component, but I don't want to use component; it looks worse, and I'm not going to settle for it. My NEC 20WMGX2 monitor is DVI only, so I couldn't test the popping, but the channel changing from SD to HD and vice versa is so much faster and smoother visually than on the Sony TV, it makes the Sony look like a piece of junk.

Before I return this TV, I'd appreciate learning if this is typical behavior, or maybe this model of the 2008 line-up is just plain flawed. I believe I can still get last year's KDL-32S3000, but I'd hate to bring it home just to find out this is standard behavior for Sonys. I don't have much experience with other HDTVs, so I'd also appreciate hearing what typical transition times are for SD/HD channel transitions when connected via HDMI to cable boxes such as I have, and whether or not there are any audible glitches, for brands other than Sony.

The secret is to keep it from doing that. Setting my DVR to "4:3 Sidebar" causes it to output SD channels in 1080i, just like the HD channels, and now channel changing is reasonably smooth. I have to partially retract what I said about the DVD player (also a Sony) being "flawless"; turning it off causes the TV to emit a pop.

You don't want 4:3 displayed as 480p, because the TV glitches when switching between 1080i and 480x. My DVR uses the term "4:3 Sidebar" to mean, "Display SD channels in 1080i". So you need to figure out how to get your set-top box to output the same resolution for both SD and HD channels.

It's really sad that the people at Sony, Cox, and Best Buy all failed to suggest this as the cause of the problem. Thinking back, I know someone who bought a 32" XBR Sony in Aug-2006, and I remember that TV exhibiting a very slow, glitchy, clumsy transition between SD and HD channels, similar to what the M4000 does (but no pop, IIRC). It must have been due to the same thing.