Back in November of 2008, I purchased a 42LG30 from Best Buy (it came with a sweet bundle deal with an LG 5.1 surround sound DVD/stereo). I have always had problems with audio synch issues using both HDMI and Component cables with the TV. There is signifcant delay with my cable/dvr box, Wii and PS2. If I run audio directly from the cable box to the stereo (and bypass the TV), then I have no noticeable delay issues, however the video game systems continue to have delay issues. I only have one digital audio input on the stereo, so it's much more convenient to run everything into the TV and take the 1 digital output from the TV and run it to the stereo.
Anyway, about 2 weeks ago, I called up LG and explained the issue to them, and they said they've had numerous complaints with this issue and said they'd send out a software update on a USB Drive right away. It showed up about a week later, but unfortunately would not work with the TV. The USB input on the TV says "service only" (unlike the more expensive models, I can't view pictures and such with the USB input on this particular TV). I emailed them back and explained the problem and within about 3 days another USB Drive showed up in the mail...same problem.
I don't know what to do at this point, but I thought I'd share that I had the same problem as other posters, and tried to fix it as some of the other posters had done with no success. I'm still waiting to hear back from LG about the latest failure...if it ever gets fixed, I'll report back.