I would like to offer my experience with the LHB975 wireless speaker synchronization problem.
After about 18 months I noticed that my rear speakers no longer worked. The red light on the rear receiver would not turn blue. After several tries going through the sync procedure in the owner's manual without success, I turned to the internet for some help. Although I found dozens of people with this problem (some had the sync problem with both the sub-woofer and the rear speakers), the vast majority had it with only with one or the other. Since the unit was out of warranty, (LG will not recognize this as a defect in the system and extend the warranty) I had no choice but to do it myself, or pay some exorbitant amount to have it fixed.
As you read this, keep in mind that this fix is for units that either one or the other wireless device is not working. If both are not working the problem probably lies somewhere else.
It turns out that the fix is quite simple if you have a little mechanical ability. The toughest part of the fix is opening the rear wireless receiver! The sub-woofer is very easy to open. (Do I have to tell you to unplug the units you are working on?)
The key to this fix if the fact that BOTH devices use the same wireless receiver card (LG P/N: EBR65859702) to receive their signal. This card is easily identified on the receiver board in that it is elevated, held on by 3 silver screws and is connected by a ribbon cable. To confirm that this part is the problem, simply swap the cards between the devices (make sure you identify the suspected bad one with a piece of tape to prevent them from getting mixed up). If the problem is fixed by swapping the cards, simply order another (about $50 + shipping, not cheap, but beats sending it out).
For an exploded diagram of these units and a parts list, go to the Sears parts web site.
Hope you have the same success I did.
Edited by jerseyfind - 10/7/12 at 12:59pm