I wasn't prepared for this today, as I didn't have my March 2008 Zenith converter or my second coupon with me. While out shopping, I checked a nearby Circuit City for any new shipments. They had a stack of DTT900 converters with an April 2008 manufacture date.
I took a chance and purchased one at the normal $59.99 price, with the understanding that it could be returned for full credit, or processed as an "exchange" with my second $40 coupon, if it worked properly.
The cover was removed upon returning home, and the main board had what appeared to be the same revision number as the previous three Zeniths that I've had. Not expecting anything different, I plugged it in and went through the setup routine.
The left channel audio issue is, happily, ***not present*** in this Zenith...the first of four to work as expected when the output is set for stereo. Multiple stations have been tried, including consistent offenders, with no problem whatsoever.
There's one other difference, which was my first tipoff that something inside of this model was different. The signal strength indicator beeps at intervals that are noticeably farther apart from each other, even with strong signals, compared to the previous three Zeniths, which were manufactured in January, February, and March 2008.
LG has apparently listened and responded...now, if only someone at their organization would make Zenith customer service aware of this.