I've always had problems with the HDMI support in my 5060N. I think it was too early for LG/HP. Many HDMI sources won't work with my display ... at least they won't pass audio.
If you want to drive these sets from a modern HDMI device, you are probably best off getting an HDMI to VGA adapter. Both Sabrent and StarTech made them and they are still on the shelves of CompUSA / TigerDirect stores today. They take HDMI in and output stereo and VGA which can be broken out into component cables for feeding your HP display.
As of last Friday though, these devices have disappeared from online stores, eBay, etc. I think the ones on the shelves at retailers will be the last you will see of them. They violate the HDCP agreement and so Intel and Warner Brothers sued the makers last week.HDCP Suit
Nonetheless, they will enable you to extend the life of your HP5060N or other older HP television if you're using more recent HDMI based Blu-Ray players, cable boxes, or whatever. The component inputs on these sets work just fine as do the RCA audio inputs. There's no reason to toss a 50"plasma display over the horrendously poor HDMI implementation.